if someone hurts you...and you don't forgive them (after awhile i mean, eventually) i think it makes you feel that you retain power over them in a way. withholding forgiveness is like you have the upper hand or something, you are in control in the relationship. when really you are not in control at all, you just want to feel like you have some control. you don't realize that this is the case, but i think deep down that is probably what is going on.