ONCE IN A WHILE I will receive an email like the following from someone who is worried that some sin they have committed may have crossed the place of no return to God’s favor.

Visitor: Even after I was sealed for the day of redemption, I still have sinned against God. I continue to fight addicting sin(s), and though most of the time I defeat the sin, sometimes I foolishly give in to it. I’m so sorry that I have given in to foolish and sinful lusts, and all I want to do is to cast away those actions forever, and to be forgiven, and sin no more. But I don’t know if I am saved anymore, because I have really been scared that my repentance is not true, because I have again sinned, and that God has cast me away. Please help me, because I am very scared. I want to be forgiven and be different.

Response: REMEMBER, your sin is not greater than Christ’s grace and work. Having been united to Christ, the Spirit of adoption can no longer come to you in a Spirit of bondage and fear because in Christ you no longer stand in your own sins, merit or performances, but are clothed in His righteousness. Because of Jesus you are already on the other side of justice and it can no longer have you (Rom 8:1). No condemnation for you in Christ for the full justice of God has been satisfied.

Christ’s once for all sacrifice means there is no longer necessary a sacrifice for sin year after year (as in Leviticus) but now His atoning work is sufficient for all time for you before God. Remember, you can neither attain, nor maintain, your right standing before God. You never did and never will, for sin cannot dissolve the covenant which God has graciously granted you in Christ. Now as always, our only hope is Jesus Christ. When God justified you, He did not then, and does not now, look at you but rather, at the covenant He made with you in Christ.

CONSIDER, when God made the covenant of grace with Abraham, God made Abraham sleep and God himself walked through the divided animals and so promised to take on Himself the punishment if Abraham did not fulfill his side of the covenant. And so it was, the seed of Abraham (that’s us) all failed to keep the covenant and so God Himself came in the flesh to fully bear up the punishment we justly deserve for not keeping our side of it. Jesus Kept it for us. He did for us what we could not do for ourselves, from our side. We are justified for His sake, not for anything God sees in us or will see in us.

It was not your obedience, repentance or faith that caused God to justify you because none of these things can pay for sin – not now, not ever. Only Christ alone can save and pay for sin. And He did. Your safety is based, therefore, on Christ’s merit, not on what you do, otherwise you are looking in your self for confidence before God, rather than Christ. No one, not one of us would have confidence if we had only to look to ourselves. So look to Christ. Herein is the gospel.

And if one thinks they can lose their salvation because of some sin they committed, they are essentially saying that what Christ did for them is insufficient. They are looking to Christ PLUS their keeping of the Law. It misses the whole point of the gospel which is that Christ saves from first to last. The passage that warns the Hebrews against falling away is warning them against one thing: abandoning trust in Christ alone by going back to now worthless and obsolete things, such as trusting in the temple sacrifice and the Law in order to be justified. The warnings in Hebrews are given to those in the covenant community that they would not be tempted to turn from trusting Jesus alone (who is God over all) for some lesser or meaningless ritual act or law keeping that supposedly now can curry God’s favor. Trusting in anything except Christ alone, who is the light that scatters all shadows, is said to be tantamount to “trampling under foot the Son of God”, that is, believing that His once of all sacrifice is insufficient in itself to save.

If something in place of, or in addition to, Jesus is trusted in it is no different than a denial of Him. So in context, the persons who go back by trading in Christ for the now-empty ritual of the temple (that itself was meant to point to the fulfillment in Christ), are then re-crucifying the Son to their shame. But unfortunately, Hebrews 6:4-8 is often read in isolation apart from this context.

IN FACT THIS IS A BACKDOOR to the Galatian heresy where Paul says, “Having begun by the Spirit, are you now being perfected by the flesh?” (Gal 3:3) To believe one can lose salvation, therefore, is trusting in something other than Jesus Christ to keep you righteous in Him. The Hebrews were tempted to go back to temple sacrifice (trusting in something other than Christ) and the doctrine that one can lose salvation is likewise trusting in ones’ own moral ability to maintain a just standing before God, since Jesus, according to them, is unable to save completely those who He came to save. Either we are trusting in Christ alone to both attain and maintain our justification or we are trusting in something worthless which the author of Hebrews gives severe warnings about. Quite ironic. That passage is a warning passage for the very error those who teach we can lose salvation are making.

So if your faith is in him today, no matter what you have done your sins are forgiven. As surely as God is good, in Christ’s blood He remembers to never treat you as your sins justly deserve because justice has already been carried out (past tense) for them. You have been set free in Christ and have been given a new heart that loves God. We trust and obey Christ, not in order to be saved but because He has saved us already. May he grant you a Spirit of revelation and an increasing knowledge of Him that your affection for Him would overcome all other vain affections.

Note: Let me just mention as an aside that your concern, your fight against sin and your sorrow for sin give witness that the Spirit is at work in you, for your would be indifferent to sin if you were unregenerate or in the flesh. A. W. Pink once wisely said, “It is not the absence of sin but the grieving over it which distinguishes the child of God from empty professors.” 

Jeremiah Burroughs declared, “… a true sorrow for sin, true repentance, is a continual act that must abide all our lives.” 

The apostle Paul said, “As it is, I rejoice, not because you were grieved, but because you were grieved into repenting. For you felt a godly grief, so that you suffered no loss through us.” (2 Cor 7:9).

Regarding sin and confession for believers again Paul said,“if we judged ourselves truly, we would not be judged.  But when we are judged by the Lord, we are disciplined so that we may not be condemned along with the world.” (1 Cor 11:31)

This demonstrates that a regenerate believer either confesses sin or the Spirit disciplines us until we feel sorrow for it, for in doing so He promises to preserve us and never let us go.

( Article Source: https://www.monergism.com/blog/my-sin-makes-me-worry-if-i-am-really-saved-0)