I enjoyed this article in Outside magazine about Misogi. This paragraph about what my older mountaineering friends call "suffering" struck me as particularly accurate:
But something funny happens once you’ve been in the grip of a painful ordeal for a certain amount of time. Namely, the body and mind—inured to the unwelcome task they’ve been set upon—mostly stop fighting it. Resisting takes too much energy. It cannot be sustained. And, gradually, in place of my instinctive resistance came an active kind of relaxation and acceptance.This definitely happens to me when backpacking or approaching climbs in the mountains. Invariably I'm in pain of some kind -- my knees, my shoulders from the pack, altitude, it's always something -- and I just grind on and on. It's slightly different from paddling, which puts me in a distinct zone I call "machine" mode, where I'm lustily pounding at some physically exerting thing for hours with my brain finally shut up.