If the Sacrament of Confirmation gives the gift of fortitude, why are we still afraid to do the right thing?
The short answer is that our human nature is still damaged because of sin, both original sin and actual sins.
Before getting into more details of this question, let us see what the Catechism of the Catholic Church has to say on the effects of confirmation.
1302 It is evident from its celebration that the effect of the sacrament of Confirmation is the full outpouring of the Holy Spirit as once granted to the apostles on the day of Pentecost.
1303 From this fact, Confirmation brings an increase and deepening of baptismal grace:
it roots us more deeply in the divine filiation which makes us cry, "Abba! Father!";115
it unites us more firmly to Christ;
it increases the gifts of the Holy Spirit in us;
it renders our bond with the Church more perfect;116
it gives us a special strength of the Holy Spirit to spread and defend the faith by word and action as true witnesses of Christ, to confess the name of Christ boldly, and never to be ashamed of the Cross:117
Recall then that you have received the spiritual seal, the spirit of wisdom and understanding, the spirit of right judgment and courage, the spirit of knowledge and reverence, the spirit of holy fear in God's presence. Guard what you have received. God the Father has marked you with his sign; Christ the Lord has confirmed you and has placed his pledge, the Spirit, in your hearts.118
1304 Like Baptism which it completes, Confirmation is given only once, for it too imprints on the soul an indelible spiritual mark, the "character," which is the sign that Jesus Christ has marked a Christian with the seal of his Spirit by clothing him with power from on high so that he may be his witness.119
1305 This "character" perfects the common priesthood of the faithful, received in Baptism, and "the confirmed person receives the power to profess faith in Christ publicly and as it were officially (quasi ex officio)."120
This sacrament completes that of baptism and confirms us in grace.
Original sin and actual mortal sin destroys sanctifying grace in our souls. Baptism restores sanctifying grace to the souls. However our human nature remains damaged due to original sin and actual sin.
Concupiscence.- This rebellion of the lower appetite transmitted to us by Adam is an occasion of sin and in that sense comes nearer to moral evil. However, the occasion of a fault is not necessarily a fault, and whilst original sin is effaced by baptism concupiscence still remains in the person baptized; therefore original sin and concupiscence cannot be one and the same thing, as was held by the early Protestants (see Council of Trent, Sess. V, can. v).
Thus actual sins weaken our abilities to resist future evils and temptations and induces us to commit greater sins; thus making it harder to stay in the state of sanctifying grace.
Although sanctifying grace has been restored to our souls through the sacrament of baptism and we are strengthened through the graces received in the sacrament of confirmation, we must still work out our individual salvation. The sacrament aid us in becoming saints, but we must still do our part in fortifying our souls through all means the Church places at our disposal, such as the sacraments of the Eucharist and Confession.
Sin is terrible and continuously weekends our human nature while the sacraments do the opposite. The Catechism of the Catholic Church can shed some light on this:
1714 Man, having been wounded in his nature by original sin, is subject to error and inclined to evil in exercising his freedom.
1854 Sins are rightly evaluated according to their gravity. The distinction between mortal and venial sin, already evident in Scripture,129 became part of the tradition of the Church. It is corroborated by human experience.
1855 Mortal sin destroys charity in the heart of man by a grave violation of God's law; it turns man away from God, who is his ultimate end and his beatitude, by preferring an inferior good to him.
Venial sin allows charity to subsist, even though it offends and wounds it.
1856 Mortal sin, by attacking the vital principle within us - that is, charity - necessitates a new initiative of God's mercy and a conversion of heart which is normally accomplished within the setting of the sacrament of reconciliation:
When the will sets itself upon something that is of its nature incompatible with the charity that orients man toward his ultimate end, then the sin is mortal by its very object . . . whether it contradicts the love of God, such as blasphemy or perjury, or the love of neighbor, such as homicide or adultery. . . . But when the sinner's will is set upon something that of its nature involves a disorder, but is not opposed to the love of God and neighbor, such as thoughtless chatter or immoderate laughter and the like, such sins are venial.
1872 Sin is an act contrary to reason. It wounds man's nature and injures human solidarity.
The sacrament of confirmation helps us to live our lives as saints, but we must at the same time cooperate with those very same graces received on the day we were confirmed by our local ordinaries (bishops).
Actual sin primarily consists in a voluntary act repugnant to the order of right reason. The act passes, but the soul of the sinner remains stained, deprived of grace, in a state of sin, until the disturbance of order has been restored by penance. This state is called habitual sin, macula peccati. reatus culpæ (I-II:87:6).
Since our human nature has been damaged by original sin and actual sin; the sacraments of baptism and confirmation are there to restore us to God’s sanctifying grace and to give us the graces necessary to remain holy. We must strive to do our part and be docile to the Spirit of Holiness and cooperate with the graces infused into our soul by the Holy Spirit in the sacrament of confirmation.
In closing, we must also keep in mind that the Devil is always seeking way to make us fall, whether that be or through fear of some other motivation.
If the Sacrament of Confirmation gives the gift of fortitude, why are we still afraid to do the right thing?
This can be more clearly explain by examples using the life of Adam, Jesus and Mary but all this people have perfect nature and do not have wounded nature, so we need St.Paul as a perfect example to answer your specific question "why are we still afraid to do the right thing?
Adam has a perfect human nature and received the gifts of the Holy Spirit just like the Sacrament of Confirmation bestowed upon all of us. But, Adam has an advantage over us because his nature is not wounded. Did Adam having perfect nature and having the gifts of original holiness and original justice able to do the right thing? The answer is NO!, Adam fall and did not do the right thing which is to obey God's Will having known fully God's Word thru His clear commandment "Do not eat the fruit of TOKAGE".
Jesus also, having a perfect human nature in the order of grace and having a sinless body like Adam, and received the fullness of the seven gifts of the Holy Spirit in the Baptism in the Jordan River, had shown that even a perfect human "struggled" to do the right thing esp. in very difficult moments.
How about Mary, also having a sinless body and a human nature that was healed in the order of grace, did Mary "struggled" like Jesus to do the right thing? In the mystery of the Incarnation it seems that there was no struggle to do the right thing, Mary only was "troubled" in the angel's greeting and was a little confused about how can She conceived a child without knowing a man. Mary after an Archangel visited Her confirming that She was "full of grace". Mary having the fullness of the seven gifts of the Holy Spirit like the Sacrament of Confirmation, had uttered Her famous Fiat and did the right thing because of "trusting faith" in the love,mercy and goodness of the Abba Father as evident in Her Magnificat.
So, where can we Adam's descendant identifies more clearly in the question "why are we still afraid to do the right thing? St.Paul is a perfect model for us because St.Paul was baptized and received the Sacrament of Confirmation like us and the most important thing of all is, St.Paul had a wounded nature like us.
Did St.Paul able to do the right thing all the time having received the gifts of the Holy Spirit? St.Paul humble admission showed No, St.Paul did not do the right thing all the time.
Romans 7:15-20 New International Version (NIV) 15 I do not understand what I do. For what I want to do I do not do, but what I hate I do. 16 And if I do what I do not want to do, I agree that the law is good. 17 As it is, it is no longer I myself who do it, but it is sin living in me. 18 For I know that good itself does not dwell in me, that is, in my sinful nature.[a] For I have the desire to do what is good, but I cannot carry it out. 19 For I do not do the good I want to do, but the evil I do not want to do—this I keep on doing. 20 Now if I do what I do not want to do, it is no longer I who do it, but it is sin living in me that does it.
So, St.Paul personal experienced and humble admission is the direct answer to your question "If the Sacrament of Confirmation gives the gift of fortitude, why are we still afraid to do the right thing?
Romans7:15-20 is the answer to your question.
To help us understand, how can we do the right things like Jesus and Mary was able to do "all the time" even if we are confused, troubled and deeply struggling because the struggles & difficulties involves sacrificing our very own life thru humiliation,persecutions,passions, crucifixion and even death. Jesus had shown every baptized believer who received the Sacrament of Confirmation or the seven gifts of the Holy Spirit including "fortitude".
The answer can be found in Jesus Christ in the Temptation in the Desert, and magnified in the Garden of Gethsemane.
Temptation in the Desert
After Jesus received the anointing of the Holy Spirit, the fullness of the gifts, the Holy Spirit led Jesus in the desert.
Jesus Is Tested in the Wilderness(Luke4:1-13)
4 Jesus, full of the Holy Spirit, left the Jordan and was led by the Spirit into the wilderness, 2 where for forty days he was tempted[a] by the devil. He ate nothing during those days, and at the end of them he was hungry.
3 The devil said to him, “If you are the Son of God, tell this stone to become bread.”
4 Jesus answered, “It is written: ‘Man shall not live on bread alone.’[b]”
5 The devil led him up to a high place and showed him in an instant all the kingdoms of the world. 6 And he said to him, “I will give you all their authority and splendor; it has been given to me, and I can give it to anyone I want to. 7 If you worship me, it will all be yours.”
8 Jesus answered, “It is written: ‘Worship the Lord your God and serve him only.’[c]”
9 The devil led him to Jerusalem and had him stand on the highest point of the temple. “If you are the Son of God,” he said, “throw yourself down from here. 10 For it is written:
“‘He will command his angels concerning you to guard you carefully; 11 they will lift you up in their hands, so that you will not strike your foot against a stone.’[d]”
12 Jesus answered, “It is said: ‘Do not put the Lord your God to the test.’[e]”
13 When the devil had finished all this tempting, he left him until an opportune time.
We can see in this passages, that Jesus having all the gifts of the Holy Spirit "did the right thing" because He knows the "word of God".
How about in the Garden of Gethsemane?
36 Then Jesus went with his disciples to a place called Gethsemane, and he said to them, “Sit here while I go over there and pray.” 37 He took Peter and the two sons of Zebedee along with him, and he began to be sorrowful and troubled. 38 Then he said to them, “My soul is overwhelmed with sorrow to the point of death. Stay here and keep watch with me.”
39 Going a little farther, he fell with his face to the ground and prayed, “My Father, if it is possible, may this cup be taken from me. Yet not as I will, but as you will.”
Jesus Christ in this passage was struggling "to do the right thing" which is to follow the Will of the Father.
Did Jesus was able to "do the right thing" ? Yes! Jesus was deeply struggling to do the right thing eventhough He was full of the gifts of the Holy Spirit. But Jesus like His beloved Mother Mary "trusted" the Abba Father, His "trusting faith", that the Will of the Father must prevails over his human will is the "right thing to do". Jesus like the Blessed Virgin Mary uttered a Fiat.
In closing, St.Paul Romans7:15-20 had shown us why we cannot do the right thing all the time. But Jesus Christ had shown thru His life that receiving the "gifts of the Holy Spirit" is not enough, we must study and know the "word of God"and in our deepest trial must surrender our will by trusting the Will of the Father is the right thing to do.
To do the right thing "all the time" we need to study and ponder the life of Jesus and Mary, and the perfect way to do it is, to follow the Will of the Father John6:40 by "Beholding the Son" and following the command of Jesus agonizing at the Foot of the Cross, saying "Son, Behold your Mother" (John19:27).