Dum Spiro Spero

There is legitimate guilt that is removed through repentance and restitution, and there is irremediable guilt.  When people say, "I know God forgives me, but I can't forgive myself," they mean that they have failed an idol, whose approval is more important to them than God's.  Idols function like gods in our lives, and so if we make career or parental approval our god and we fail it, then the idol curses us in our hearts for the rest of our lives.  We can't shake the sense of failure.

~Timothy Keller, Counterfeit Gods, p. 149