ron athey:

I think if you're boiling inside, the strongest manifestation you can make is to physically abuse yourself - and if you know why you're doing it, you can transcend and work through it. If you deny why you're doing it, the problems can perpetuate themselves.

eg. a friend gave me a ritual whipping over grieving. I wouldn't call this masochism. I was filled with so much sorrow because 3 friends had just died. She beat me for half an hour until I cried, focusing on the loss, not the sensuality of it or the submission.