Falling.
Well, this today was hard core.The way up was bad enough, just staring straight ahead at the steps in front of me. The teacher had told us that if we really didn't want to go up, we didn't have to and halfway up when I started to get really scared, I considered stopping and going back down. I guess my vanity helped me out, because I kept thinking, "If I stop, everyone behind me on the stairs is going to have to go back down and then up again and I'm going to look like a fool in front of the whole class," and that kept me forging ahead. But the way down was absolutely terrifying because the only choices you had were to either look down (unthinkable) or look straight out into the wide open space, which made my legs feel wobbly and my eyes tear up. I took it slow, and I made it.
I thought actually being up there would be the worst part of it -- and it was pretty intense standing on a grid of steel pipes with 4 or 5 inch spaces between them looking straight down 65 feet to the stage floor -- but the walk up and down were far worse. It's one thing to stand still and involuntarily contemplate, over and over feeling it in your bones every time, falling, but there's something altogether more difficult about forcing yourself to put one foot in front of the other when every nerve and muscle in your body is telling you that to move means death.