Why do People Cut Themselves?

[Lunarian]

Maybe it's not the same and it's just an autism thing, but I hit myself or bang my head on something when I get upset. I just get so upset and angry that I just get the impulse to hit myself. I feel like I deserve it too. To be hurt like that and punished. Too scared to cut myself though. I'm afraid I'll do it too much and blood really scares me..