Both the apostle Peter and the apostle Judas betrayed Jesus. Peter denied he knew Jesus. Judas revealed Jesus' identity to Roman guards intending to execute him.
After Peter denied he knew Jesus, he realized what he had done and "wept bitterly." Peter processed his sin and showed remorse through his tears. We can assume that he forgave himself from the Scripture.
After Judas realized his sinful acts, he ran away and killed himself. Judas felt so guilty about his betrayal of Jesus and felt so useless that he killed himself.
Peter forgave himself, Judas killed himself. As a result, God was able to use Peter to preach to Gentiles and spread the Word. God was not able to use Judas at all.
I, like everyone else, have committed acts for which I feel guilty. I have sinned. When I allow myself to feel guilty, I end up believing I am unworthy and useless. God cannot use me when I am wallowing in guilt and despair.
Yet if I forgive myself, I can move on from the sinful act and be used by God.
This post was inspired by the book "The Mother Load" by Mary M. Byers.