Man can never truly be liberated from concupiscence and thereby possess a sinless body, while on earth. But he can make great strives towards perfection towards union with God.
Well, while on earth it takes a lot and I mean a lot of hard work, patience, fortitude and guidance from an excellent spiritual director gifted in the arts of the spiritual life.
The Church calls this the Way of Perfection and is normally divided into three stages: the purgative way, the illuminative way and the unitive way.
The purgative way
The purgative way is the way, or state, of those who are beginners, that is, those who have obtained justification, but have not their passions and evil inclinations in such a state of subjugation that they can easily overcome temptations, and who, in order to preserve and exercise charity and the other virtues have to keep up a continual warfare within themselves. It is so called because the chief concern of the soul in this state is to resist and to overcome the passions by nourishing, strengthening, and cherishing the virtue of charity. This can and ought to be done not only by keeping the Commandments, but by foreseeing the occasions in which the precepts oblige, so as to be ready by a prompt and well disposed will to resist and avoid any sins opposed to them. This state, although, in one sense, it is imperfect, in another sense may be called a state of perfection, because the soul remains united to God by grace and charity so long as it is free from the stain of mortal sin. Purity of soul may be said to be the proper end of the purgative way, and the forms of prayer suitable for this way or state are meditations on sin and its consequences, and on death, judgment, hell, and heaven. The acts which aid toward uprooting the remnants and habits of former sins, and preventing one from ever returning to them, are corporal austerities, mortification of the appetite, abnegation of one's own will, and conformity to the will of God. In a word, the distinctive notes of this state are war against those temptations which entice the soul to sin by the attraction of pleasures of the senses and the natural shrinking from pain; and repugnance to acts known to be contrary to the will of God. The characteristic virtue of this state is humility, by which the soul is made sensible of its own weakness and its dependence upon the succours of the grace of God.
What mystical writers describe as the active and passive purifications of the spiritual life may be brought under, and arranged according to, their three states of perfection, though not confined to any one of them. The active purification consists of all the holy efforts, mortifications, labors, and sufferings by which the soul, aided by the grace of God endeavors to reform the mind, heart, and the sensitive appetite. This is the characteristic work of the purgative way. The passive purifications are the means which God employs to purify the soul from its stains and vices, and to prepare it for the exceptional graces of the supernatural life. In the works of St. John of the Cross these purifications are called nights, and he divides them into two classes, the night of the senses and the night of the spirits. In the state of beginners the soul is often favored by God with what are called "sensible consolations" because they have their beginning and are felt chiefly in the senses or sensible faculties. They consist in sensible devotion and a feeling of fervour arising from the consideration of God's goodness vividly represented to the mind and heart; or, from external aids, such as the ceremonies of the Church. These consolations are often withdrawn, and a state of desolation ensues, and then the passive purification of the senses begins.
The illuminative way
The illuminative way is that of those who are in the state of progress and have their passions better under control, so that they easily keep themselves from mortal sin, but who do not so easily avoid venial sins, because they still take pleasure in earthly things and allow their minds to be distracted by various imaginations and their hearts with numberless desires, though not in matters that are strictly unlawful. It is called the illuminative way, because in it the mind becomes more and more enlightened as to spiritual things and the practice of virtue. In this grade charity is stronger and more perfect than in the state of beginners; the soul is chiefly occupied with progress in the spiritual life and in all the virtues, both theological and moral. The practice of prayer suitable for this state is meditation on the mysteries of the Incarnation, the life of Our Savior, and the mysteries of His Sacred Passion. As Ven. Luis de Lapuente says,
Though the mysteries of the Passion belong to the illuminative way, especially in its highest degree, which approaches nearest to the unitive way, nevertheless, they are exceedingly profitable for all sorts of persons, by whatever way they walk, and in whatever degree of perfection they live; for sinners will find in them most effectual motives to purify themselves from all their sins; beginners to mortify their passions; proficients to increase in all kinds of virtue; and the perfect to obtain union with God by fervent love. (Introduction to "Meditations on the Passion")
The fundamental virtue of this state is recollection, that is, a constant attention of the mind and of the affections of the heart to thoughts and sentiments which elevate the soul to God — exterior recollection which consists in the love of silence and retirement, interior recollection in simplicity of spirit and a right intention, as well as attention to God in all our actions. This does not mean that a person has to neglect the duties of his state or position in life, nor does it imply that honest and needful recreation should be avoided, because these lawful or necessary circumstances or occupations can well be reconciled with perfect recollection and the most holy union with God.
The soul in the illuminative way will have to experience periods of spiritual consolations and desolations. It does not at once enter upon the unitive way when it has passed through the aridities of the first purgation. It must spend some time, perhaps years, after quitting the state of beginners in exercising itself in the state of proficients. St. John of the Cross tells us that in this state the soul, like one released from a rigorous imprisonment, occupies itself in Divine thoughts with a much greater freedom and satisfaction, and its joy is more abundant and interior than it ever experienced before it entered the night of the senses. Its purgation is still somewhat incomplete, and the purification of the senses is not yet finished and perfect. It is not without aridities, darkness, and trials, sometimes more severe than in the past. During the period of desolation it will have to endure much suffering from temptations against the theological virtues and against the moral virtues. It will have to endure sometimes other diabolical attacks upon its imagination and senses. Also, God will permit natural causes to combine in afflicting the soul, such as the persecutions of men, and the ingratitude of friends. Patient suffering and resignation have to be borne during all these trials, and the devout soul should remember the encouraging words of the pious and learned Blosius:
Nothing more valuable can befall a man than tribulation, when it is endured with patience for the love of God; because there is no more certain sign of the divine election. But this should be understood quite as much of internal as of external trials which people of a certain kind of piety forget.
And again he says,
It is the chain of patient suffering that forms the ring with which Christ espouses a soul to Himself. (Institutio Spiritualis, viii, 3)
The unitive way
The unitive way is the way of those who are in the state of the perfect, that is, those who have their minds so drawn away from all temporal things that they enjoy great peace, who are neither agitated by various desires nor moved by any great extent by passion, and who have their minds chiefly fixed on God and their attention turned, either always or very frequently, to Him. It is the union with God by love and the actual experience and exercise of that love. It is called the state of "perfect charity", because souls who have reached that state are ever prompt in the exercise of charity by loving God habitually and by frequent and efficacious acts of that Divine virtue. It is called the "unitive" way because it is by love that the soul is united to God, and the more perfect the charity, the closer and more intimate is the union. Union with God is the principal study and endeavor of this state. It is of this union St. Paul speaks when he says: "He who is joined to the Lord, is one spirit." (1 Corinthians 6:17). Souls thus united to God are penetrated by the highest motives of the theological and moral virtues. In every circumstance of their lives the supernatural motive which ought to guide their actions is ever present to their mind, and the actions are performed under its inspiration with a force of will which makes their accomplishment easy and even delightful. These perfect souls are above all familiar with the doctrine and use of consolations and desolations. They are enlightened in the mysteries of the supernatural life, and they have experience of that truth proclaimed by St. Paul when he said: "We know that to them that love God, all things work together unto good, to such as, according to His purpose, are called to be saints." (Romans 8:28). The form of prayer suitable to persons in the unitive way is the contemplation of the glorious mysteries of Our Lord, His Resurrection, Appearances, and Ascension, until the coming of the Holy Ghost, and the preaching of the Gospel. These mysteries may also be the subject of meditation for beginners and for those in a state of progress, but in a peculiar manner, they belong to the perfect. Union with God belongs substantially to all souls in a state of grace, but it is in a special manner the distinguishing characteristic of those in the unitive way or in the state of the perfect.
It is in this state that the gift of contemplation is imparted to the soul, though this is not always the case; because many souls who are perfect in the unitive way never receive in this life the gift of contemplation and there have been numerous saints who were not mystics or contemplatives and who nevertheless excelled in the practice of heroic virtue. Souls, however, who have attained to the unitive state have consolations of a purer and higher order than others, and are more often favored by extraordinary graces; and sometimes with the extraordinary phenomena of the mystical state such as ecstasies, raptures, and what is known as the prayer of union.
The soul, however, is not always in this state free from desolations and passive purgation. St. John of the Cross tells us that the purification of the spirit usually takes place after the purification of the senses. The night of the senses being over, the soul for some time enjoys, according to this eminent authority the sweet delights of contemplation; then, perhaps, when least expected the second night comes, far darker and far more miserable than the first, and this is called by him the purification of the spirit, which means the purification of the interior faculties, the intellect and the will. The temptations which assail the soul in this state are similar in their nature to those which afflict souls in the illuminative way, only more aggravated, because felt more keenly; and the withdrawal of the consolations of the spirit which they have already experienced in their greatest affliction. To these trials are added others, peculiar to the spirit, which arise from the intensity of their love for God, for Whose possession they thirst and long. "The fire of Divine love can so dry up the spirit and enkindle its desire for satisfying its thirst that it turns upon itself a thousand times and longs for God in a thousand ways, as the Psalmist did when he said: For Thee my soul hath thirsted; for Thee my flesh O how many ways" (St. John of the Cross, op. cit. infra, bk. II, xi). There are three degrees of this species of suffering designated by mystical writers as the "inflammation of love", the "wounds of love", and the "langour of love". - State or Way (Purgative, Illuminative, Unitive)
When starting out in the true spiritual life and trying as Christian to be freed from concupiscence and thereby possess a sinless body, the purgative way is indeed the hardest and longest to obtain. Because of this, most do not prevail past this stage. This first stage requires one to purify oneself of as much personal sin as possible through penance, sacramental confession and sound spiritual advice from a spiritual director. This is a hard and forceful stage.
For those who can read French, I would highly recommend Mother Cécile Bruyère‘s book La vie spirituelle et l'oraison. It is based on both solid Catholic doctrine and tradition, as well as by personal experience in a monastic setting.
Fr. Reginald Garrigou-Lagrange, OP writes in a more formal style, true to being as great theologian and a university professor at the Dominican Pontifical University of St. Thomas Aquinas, the Angelicum, in Rome from 1909 to 1960.