To paraphrase a very wise man:
Never feel sorry for yourself. Never allow yourself to feel as if you are worthless. Never tell yourself that you are a fool.
When one gives into these feelings, sin is inevitable. After all, how could we possibly avoid sin when we’re such hopeless and helpless fools? Such feelings are precisely what Satan desires for us because they are precisely what Satan thinks about himself. Self-pity is the favorite tool of hell.
Instead, we should readily and humbly acknowledge our nothingness while simultaneously acknowledging the infinite goodness that is Almighty God. Our merits are nothing, it is true, but His merits are eternal and infinite. Through us, nothing is possible and everything is hard. Through God, all things are possible and nothing is hard.