The answer to the question varies depending on what is going on. Most of the time it is because I want to feel less depressed, angry or other emotions I don't know how to cope with. In the place the those things I feel numb and not there. Eventually everything comes back and I am back to square one again.

Other times it is because I hate myself and it is the only way I can express it and process those feelings. Afterwards the feelings of self hate and worthlessness subside some and I am left feeling numb and in a state of shock I guess.

Other times I just want it to for no logical reason other than I just feel like I deserve it.