("explain away" presupposes this verse teaches the so-called 'once saved always saved' doctrine)
In whom you also, after you had heard the word of truth, (the gospel of your salvation;) in whom also believing, you were signed with the holy Spirit of promise, Who is the pledge of our inheritance, unto the redemption of acquisition, unto the praise of his glory.
Right off the bat, we know this is a conditional (Romans 11:22b) assurance (you can't murder someone or commit adultery,and not have that forfeit your salvation).
For if we sin wilfully after having the knowledge of the truth, there is now left no sacrifice for sins, but a certain dreadful expectation of judgment, and the rage of a fire which shall consume the adversaries. A man making void the law of Moses, dieth without any mercy under two or three witnesses: How much more, do you think he deserveth worse punishments, who hath trodden under foot the Son of God, and hath esteemed the blood of the testament unclean, by which he was sanctified, and hath offered an affront to the Spirit of grace? For we know him that hath said: Vengeance belongeth to me, and I will repay. And again: The Lord shall judge his people. It is a dreadful thing to fall into the hands of the living God.
Do not therefore lose your confidence, which hath a great reward. For patience is necessary for you; that, doing the will of God, you may receive the promise. For yet a little and a very little while, and he that is to come, will come, and will not delay. But my just man liveth by faith; but if he withdraw himself, he shall not please my soul.
Scripture doesn't make an except for Christians, who are called to a higher calling than everyone else, anywhere.
1 Corinthians 6:8-10
But you do wrong and defraud, and that to your brethren. Know you not that the unjust shall not possess the kingdom of God? Do not err: neither fornicators, nor idolaters, nor adulterers, Nor the effeminate, nor liers with mankind, nor thieves, nor covetous, nor drunkards, nor railers, nor extortioners, shall possess the kingdom of God.
Imagine St. Paul saying this if 'once saved always saved' were true. He would be saying in fact:
"But you sin against your brother. Do you not know that the unjust (but don't worry, not you) shall not inherit the kingdom of God?"
Ridiculous. It strips all meaning from the text.
So do you also reckon, that you are dead to sin, but alive unto God, in Christ Jesus our Lord.
Let not sin therefore reign in your mortal body, so as to obey the lusts thereof. Neither yield ye your members as instruments of iniquity unto sin; but present yourselves to God, as those that are alive from the dead, and your members as instruments of justice unto God. For sin shall not have dominion over you; for you are not under the law, but under grace. What then? Shall we sin, because we are not under the law, but under grace? God forbid. Know you not, that to whom you yield yourselves servants to obey, his servants you are whom you obey, whether it be of sin unto death, or of obedience unto justice.
The extensive use in of the countless imperatives of St. Paul and others in Scripture to urge us not to sin, and tells us that those who sin will go to Hell, are stripped of all their meaning by people to advocate the unbiblical doctrine of unconditional perseverence.
Heck, we are commanded to persevere (Hebrews 10:36). We aren't robots.
And because iniquity hath abounded, the charity of many shall grow cold. But he that shall persevere to the end, he shall be saved.
Hear you therefore the parable of the sower.
When any one heareth the word of the kingdom, and understandeth it not, there cometh the wicked one, and catcheth away that which was sown in his heart: this is he that received the seed by the way side. And he that received the seed upon stony ground, is he that heareth the word, and immediately receiveth it with joy. Yet hath he not root in himself, but is only for a time: and when there ariseth tribulation and persecution because of the word, he is presently scandalized. And he that received the seed among thorns, is he that heareth the word, and the care of this world and the deceitfulness of riches choketh up the word, and he becometh fruitless. But he that received the seed upon good ground, is he that heareth the word, and understandeth, and beareth fruit, and yieldeth the one an hundredfold, and another sixty, and another thirty.
For even as [a parable] a man going into a far country, called his servants, and delivered to them his goods; And to one he gave five talents, and to another two, and to another one, to every one according to his proper ability: and immediately he took his journey. And he that had received the five talents, went his way, and traded with the same, and gained other five. And in like manner he that had received the two, gained two more. But he that had received the one, going his way digged into the earth, and hid his lord's money. But after a long time the lord of those servants came, and reckoned with them. And he that had received the five talents coming, brought five more talents, saying: Lord, thou didst deliver to me five talents, behold I have gained five more over and above. His lord said to him: Well done, good and faithful servant, because thou hast been faithful over a few things, I will place thee over many things: enter thou into the joy of thy lord. And he also that had received the two talents came and said: Lord, thou deliveredst two talents to me: behold I have gained other two. His lord said to him: Well done, good and faithful servant: because thou hast been faithful over a few things, I will place thee over many things: enter thou into the joy of thy lord. But he that had received the one talent, came and said: Lord, I know that thou art a hard man; thou reapest where thou hast not sown, and gatherest where thou hast not strewed. And being afraid I went and hid thy talent in the earth: behold here thou hast that which is thine. And his lord answering, said to him: Wicked and slothful servant, thou knewest that I reap where I sow not, and gather where I have not strewed: Thou oughtest therefore to have committed my money to the bankers, and at my coming I should have received my own with usury. Take ye away therefore the talent from him, and give it to him that hath ten talents. For to every one that hath shall be given, and he shall abound: but from him that hath not, that also which he seemeth to have shall be taken away. And the unprofitable servant cast ye out into the exterior darkness. There shall be weeping and gnashing of teeth.
So our deeds aren't inconsequential in the slightest (John 15:6 et seq). Our salvation depends on continuing (Romans 11:22) in goodness.
To them indeed, who according to patience in good work, seek glory and honour and incorruption, [He gives] eternal life
In short, it isn't God who is unfaithful to His promises (John 6:37; 1 Timothy 2:4), but us who forfeit the promise ourselves (2 Timothy 2:12).
See my related answer here.