God isn't looking for us to be perfect. He's already found that perfection in our Lord and Savior Christ Jesus who made a Perfect sacrifice. One's personal sins are never as important as what our Lord Jesus Christ did on the Cross about our sins.
Repentence is simply turning back. The focus of our thinking whenever we sin, is simply on anything other than God through faith in Christ. We never sin while we are remaining in fellowship in God by believing in Him through faith in Christ.
Repentence is turning back to God. It isn't emotional. It isn't based upon our promises not to sin again. Our basis with God is upon His grace, not upon our merit or lack thereof. He doesn't base His grace upon our actions, past, present, or future, but rather upon the work of Christ on the Cross. That is the cornerstone of our faith.
The Apostle Paul used the verb hamartano when he wrote, “For all have sinned, and come short of the glory of God” (Romans 3:23).
When we sin, we fall out of fellowship with Him because we have exercised our volition independent of remaining faithful through Christ. Once this occurs, we haven't changed the will of Soverign God. He remains immutable, but we have changed ourselves. We haven't changed His sealing of our salvation, rather we change our thinking and perception of that relationship with God.
Heb 10:26-31
6 For if we go on sinning willfully after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, 27 but a certain fearful expectation of judgment and a zeal of fire that will consume the adversaries. 28 Anyone who has set aside the Law of Moses dies without mercy on the testimony of two or three witnesses. 29 How much more severe punishment do you think he will deserve who has trampled under foot the son of God, and has regarded as common the blood of the covenant by which he was made holy, and has insulted the Spirit of grace? 30 For we know him who said, "Vengeance is mine; I will repay" (Deut 32:35). And again, "The Lord will judge his people" (Deut 32:36). 31 It is a terrifying thing to fall into the hands of the living God.
The saved believer who falls into sin, does so first by exercising his own volition independent of faith through Christ. Accordingly, that person isn't believing in God through faith in Christ at the time of that sin. This doesn't remove the past sealing of God the Holy Spirit. That sealing is completely performed by the volition and Sovereign decision of God which can never be changed.
This doesn't mean though, that we don't now view our relationship with Hm differently. Now from our perspective, there remains no sacrifice for sin, therefore we simply have a fearful expectation of judgment and fiery condemnation.
So what is the solution?
The same solution for any problem we ever encounter in life for all eternity, first we believe in God through faith in Christ.
How do we do that after we already had salvation and we turn away?
Simple, we simply face God again. That is all repentence is. Repentence focuses on God, not the sin. Focusing on the sin and our guilt merely places our thinking in a situation where we are judging ourselves independently of faith through Christ. The Adversary loves it when a believer, with all the magnificient gifts of the Holy Spirit, turns away from God and begins to eat himself alive in guilt and remorse over things in the past. God, however remains faithful and true in His sanctification process of His children.
If we remain in sin, he simply disciplines us. If we further remain in sin, then He typically may discipline us with consequences seven times more severe.
The solution is simply to turn back to Him, i.e. refocus on God the Father, through faith in God the Son. Then while facing Him, confessing our sins through faith in Christ.
1st John 1:9 If we confess our sins, he is faithful and just to forgive us [our] sins, and to cleanse us from all unrighteousness.
When we confess our sins, known and unknown, while facing God the Father through faith in Christ, we end up back in fellowship with God the Holy Spirit, so that He is then in a position to freely exercise His grace and further sanctify us as we study His Word.
Thinking there is some sin we've performed is so heinous that God won't forgive us of it is fallacious. (He knew all the sins each of us would ever perform at the very moment we first believed in Him through faith in Christ and He sealed us at that very moment. Christ also died for all of our sins, not just those we think He might cherrypick from the list.)
God is faithful in forgiveness. God's faithfulness means there are no exceptions; no sin is too bad, heinous, or evil. God always does exactly the same thing on the basis of the work of Jesus Christ on the Cross. One's personal sins are never as important as what our Lord Jesus Christ did on the Cross about our sins.
What appears to have occurred here is hamartophobia.
hamartophobia
1. Fear that one will commit or has committed some grievous error or unpardonable sin.
2. An excessive fear of committing errors or sins or of doing the wrong thing and being condemned for it.
It is also known as despair-a failure to believe one can receive the Mercy of God.