I used to do this as a teenager. The thought still comes up now and then 30+ years later. It seems to be a way to focus otherwise diffuse and ambiguous and intolerable anxiety. If you can see it and feel it as you cut, you can somehow understand it.

I wonder if people who tattoo and body pierce to extreme are doing something similar. Maybe is has to do with the endorphins realeased.

It really is a horrible habit. Dangerous. Embarassing. I had to wear long sleeves for too many years to hide.