For me it's not much different than the reason you'd want to hurt anyone--to punish them. Vengeance. Just like lightning is a burst of energy balancing out the negative and positive charges. When I hurt myself, I feel I deserve it. It helps to think of me doing it to someone else: would that teach them? Help them? Motivate or encourage them? If no, then why should it make me feel better? Don't know if I'm making sense.

My distractions are doing something to benefit another person, and exercise/tasks.