You need to be honest with yourself: Are these feelings of guilt and inadequacy based in reality, or just a personality issue? Does G-d really have it in for you, or is this just the pessimism of an anxious beast inside?
If it is the latter, take a break from your self-derision and nurture confidence in the Director of this universe. He carries you through every moment, but only as close as your trust in Him will allow.
As for the personality issue, channel that in positive ways. People of such nature are generally apt to serious study, deep and creative thought, and dogged persistence.