Regret for a sinful past will remain until we truly believe that for us in Christ that sinful past no longer exists. The man in Christ has only Christ’s past and that is perfect and acceptable to God. In Christ he died, in Christ he rose, and in Christ he is seated within the circle of God’s favored ones. He is no longer angry with himself because he is no longer self-regarding, but Christ-regarding; hence there is no place for regret.
That Incredible Christian, “The Futility of Regret”