I do it for the adrenaline & endorphin; for it's ability to halt my unwelcome or uncomfortable thoughts immediately and reliably; to see the blood; for the release it brings; for the comfort it brings; because I just NEED to; to rid myself of the body memories; because my scars tingle; because it actually feels good (see the comment on the adrenaline/endorphin rush)... because maybe some day I will finally slip up enough that it will kill me by accident...