I haven't been rock climbing, but I can tell you that the main reason I'm scared of heights is because I get an urge to jump off, and I have to fight it back down again. If there's a full glass window or something between me and the drop, on the other hand, heights don't bother me at all.
ETA: There is now a third thread, so send new comments there.
Since the first thread has exceeded 500 comments, it seems time for a new one, with Eliezer's just-posted Chapter 33 & 34 to kick things off.
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