Guilt serves no purpose. The past is just that: passed! Gone. Slipped away. Not to be repeated. If you need to make restitution, then do it. If you messed up, apologize. If you are forgiven for your mistake, give thanks and move on. If you are not forgiven, move on anyway. Forgive yourself, learn from the experience, and act differently next time. At that point, it's over. Don't bother with guilt.