i'd be curious to know what people say to this too... i fell and broke my foot a few months ago and i was screaming and in utter agony-- when just a little while prior to that i was punching walls and beating myself up. It's weird how when you induce the pain on yourself, you can tolerate it, but when it's an accident, unintended, and unexpected, it actually hurts.

maybe when you cut on purpose, you're mentally prepared with endorphins to deal with the pain, but accidents catch you by surprise and your nervous system takes over (is that parasympthathetic or sympathetic? hmm).