As a psychology student, I frequently psychoanalyze myself and my methods. I was abused as a child by my mother; physically, mentally, and emotionally. And for as long as I can remember, I have been a masochist.
Psychologically all children crave attention from their parents, and the only attention I frequently recieved was abuse. So somewhere with in my mind I associate pain with feeling loved and valued, since that was all I was exposed to. And now as an adult I am easily aroused by simple acts of dominance.
It's taken awhile to make my mate understand that in the right circumstances I enjoy being hurt, but now he understands and tries to feed my fetishes.
There is nothing wrong with being a masochist, and as long as your happy with it there is no reason to change.