"...and some of the wise shall stumble, so that they may be refined, purified, and made white..." (Daniel 11:35)
It hurts to hear someone who once followed Christ has traded Him for the pleasures of the world. There are those who go astray who were never true in their repentance at the first, just as John says in 1 John 2:19. But I believe that there are true believers, too, who walk away, spend a good deal of their time saying "yes" to sin (Titus 2:12), and return, never having lost their status as "son" in Christ, but grieving the Holy Spirit all the same.
In fact, as the Prodigal Son gave everything to his momentary pleasure until he had nothing left, it is often this wallowing in sin that causes many to return to God with even greater humility and awe and joy, knowing that when they went astray, He was steady and they were "kept" (Jude 1:1).
I don't believe God revokes justification. I don't believe we keep ourselves saved by our obedience. But where does 1 John fit into this? There is a whole section expounding the fact that "no one born of God makes a practice of sinning, for God's Seed abides in him, and he cannot keep on sinning because he has been born of God."
I think the difference is understood in this: time.
There are those who never truly knew Christ, but spoke as though they did-- and maybe even believed it themselves. In the middle of all the church activities, just like those crowds who welcomed Jesus into Jerusalem shouting one day that He was their King and the next that He should die.
After these have turned to pursue the world, few return, nor do they find any reason to. All they thought they knew of God was only second-hand and disappointing. What they had in church was never any more real (and a lot less visceral) to them than the temporary highs the world has given them since they've abandoned Him and His teaching.
However, for those who do know Christ, I feel like in the back of their minds they still fight with themselves, even just a little, knowing that what they are doing won't give them the lasting fulfillment they want. They get more and more determined to misattribute the depression and fear and shame they feel and seek to override it by committing more shameful acts until one day they find they can't continue. And so they repent because, despite all the anxiety toward returning to Christ and His church, they recognize it as the only complete hope and light to be found in the world.
And that is the difference: they do come back.
They come back to the peace and joy of God found in the study and practice of His commands.
Not back to favor with God or to salvation because that can't be lost. Those who have been called and justified cannot annul the promise of being glorified (Romans 8:30). They have the promise that the work that has been started in them by God will also be brought to completion by God (Philippians 1:6). They have the Holy Spirit as a guarantee of their salvation (Ephesians 1:4), no matter how well they've managed to stifle His conviction.
Our position before God is never based on us and how well we do choosing Christ and abstaining from sin. It is based in Christ. Always and only Christ-- His holy birth, His holy life, His holy death, His holy resurrection, all "according to the Scriptures," (1 Corinthians 15:3-4) and all the basis for the new covenant (Hebrews, especially 10:11-18) through which we stand before God.
As Colossians 3:3 states, we are hidden with Christ in God. What does this mean but that the unity Jesus prayed for in John 17 has been granted-- that just as He and the Father are one, so we also may be one with each other and, all together, with Him.
We cannot be separated. The Father and Christ cannot be separated; they are One eternally. The Father turned His back on His Son on the cross as He became sin for us (1 Corinthians 5:21), but Jesus didn't cease to be the Father's Son. No, that inexorable title and nature is what caused Christ to rise from the dead in victory! In salvation, we, too-- because we are "hidden in" (within; protected, renewed, kept, and insured by) One who will never be cast away-- are ourselves never to be cast away.
Perhaps you will say that because we are hidden in Christ, we will not give in to sin again for any extended amount of time. Lord willing that will be true. But how much time is too much? For surely we all sin, and that sin takes time to commit. Is there a limit? a grace period that expires at a certain mark, after which you lose your salvation? I don't believe there to be such a scale.
Let's go back to Colossians 3, adding in Ephesians 2-4 which begins with Paul telling us that, though still physically on earth, we also are seated with Christ in Heaven. We see from the order of action in both of these passages that it is only from that position that we are able to give up sin. We are not in Christ because we are doing a good job of resisting temptation on our own. We fight to become sinless because we have been made alive in Christ, and it is only by the strength that He provides that we can obey (Philippians 2:13).
Our position doesn't change because Christ never changes, and, if we are in Him, we are protected by His perfection. He has given His perfect record to us forever. He did not wipe our slate clean at the beginning of salvation to then begin a new record of wrongs.
Yes, God knows our current sins. He isn't blind to our actions; He knows when we've gone astray. But He doesn't attach His wrath to that knowledge, "for Christ also suffered once for sins, the righteous for the unrighteous, to bring you to God." The sentence for every sin we have, are, or will commit has already been spent on Christ.
And that is why we shouldn't continue sinning.
Why Hebrews 10 goes on to say that when we sin, we have "trampled underfoot the Son of God, and profaned the blood of the covenant by which [we are] sanctified, and has treated with arrogance the Spirit of grace."
Why Hebrews 10 goes on to say that when we sin, we have "trampled underfoot the Son of God, and profaned the blood of the covenant by which [we are] sanctified, and has treated with arrogance the Spirit of grace."
How dare we disgrace that which has given us our freedom. How much greater wrath do we deserve who spitefully disregard He Who destroyed Himself, so we could be made whole in Him? What further hope do we have than Christ?
But His blood and His covenant, even in the face of great contempt, do not become ineffectual. Because God cannot deny Himself (2 Timothy 2:13), He remains faithful to the covenant He has made with His Son and with us, even when we wander.
Christ is our sacrifice, pointing to His once and for all pardon.
Christ is our King and our Judge, reminding us of His Law and writing it on our hearts, disciplining us in whatever way necessary to cause us to feel true remorse over the "sin that so easily entangles" (Hebrews 12:1) that we might return to Him in repentance.
Christ is our High Priest, "praying for us that our faith may not fail" and instructing us to "strengthen our brothers" by pointing out the deceitfulness of sin and the "surpassing worth of knowing Christ Jesus" (Philippians 3:8).
If we are truly in Christ, eventually we will listen. And when we've returned, we will have been further refined and purified through the fire of disappointment, discipline, and repentance.