There is indeed a godly sorrow that worketh repentance (2 Cor. 7:10), and it must be acknowledged that among us Christians this feeling is often not present in sufficient strength to work real repentance; but the persistence of this sorrow till it becomes chronic regret is neither right nor good. Regret is a kind of frustrated repentance that has not been quite consummated. Once the soul has turned from all sin and committed itself wholly to God there is no longer any legitimate place for regret. When moral innocence has been restored by the forgiving love of God the guilt may be remembered, but the sting is gone from the memory. The forgiven man knows that he has sinned, but he no longer feels it. The effort to be forgiven by works is one that can never be completed because no one knows or can know how much is enough to cancel out the offense; so the seeker must go on year after year paying on his moral debt, here a little, there a little, knowing that he sometimes adds to his bill much more than he pays. The task of keeping books on such a transaction can never end, and the seeker can only hope that when the last entry is made he may be ahead and the account fully paid. This is quite the popular belief, this forgiveness by self-effort, but it is a natural heresy and can at last only betray those who depend upon it.
Source: Tozer Devotional