When we look back on our old self, we tend to have a lot of regrets, and we wish we could go back and change things. As believers, we still have an “old man” living with us: our sinful nature. Paul calls us to kill this old man, putting to death the deeds of the body, and instead to follow the Holy Spirit in obedience which comes from faith.
For if you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body, you will live. For all who are led by the Spirit of God are sons of God. For you did not receive the spirit of slavery to fall back into fear, but you have received the Spirit of adoption as sons, by whom we cry, “Abba! Father!” The Spirit himself bears witness with our spirit that we are children of God, and if children, then heirs—heirs of God and fellow heirs with Christ, provided we suffer with him in order that we may also be glorified with him.Romans 8:13-17