Probably because with pain at least you feel something. People who engage in pain seeking behaviors often they do because subconsciously believe they're not worthy of positive emotions so they settle for *any* feeling. Life without any kind of feeling is pretty much the same as being dead. Negative emotions and perceptions are preferable to none at all. You need other people to validate your existence by making them cause emotion in you. If you believe nobody will ever love you or consider you worthy of friendship, as long as you haven't given up on living, at least you'll make an effort for others to acknowledge your existence by making them cause you pain.
Kind of the reason some people gets into martial arts. Even if people are going to punch you and make you feel like shit, at least they're acknowledging your existence and making you feel something.
Why haven't you joined a fight club yet? It's way better than staying at home moping around.
