We all say we can endure all the pain in the world, even though the worst pain most of us suffered was stubbing our toes in the coffee table (and even then we had to try real hard not to cry). But think about cutting your skin, then your flesh, and then your fucking bone with a butter knife. 90% of us will quit after the first slash, at the sight of blood.
But, there's one possible instance in which I might do it. If my hand was trapped under a rock, and there was this huge beast thing coming to get me from a few hundred meters away, the adrenaline boost and the fear might give me enough strength to pull it off. Otherwise, I would rather try cracking the rock with my forehead instead.