Masochism

A song to personify my disposition: By Myself (Linkin Park)

"A willingness or tendency to subject oneself to unpleasant or trying experiences"

The word to describe my situation. I think I have a propensity to do certain things which I know will result in myself feeling like crap afterwards. I'm sure this sort of behaviour is immensely unhealthy. At least the pent up frustration and pain is good for motivation at the gym.