I've developed a fear of heights. As a kid I had no fear or even respect for it really... My buddies and I would climb trees as high as we could and swing from branches, jump from second story windows, jump huge gaps/stair sets on skateboards, etc. We thought we were gonna be the next CKY or Jack@ss. There was a 40ish foot (depending on the tide) train bridge over a river in our town that we would would jump from all summer. Flips, gainers, you name it. Had a buddy that would intentionally belly flop off it if you said "you won't"... I don't know when, or what did it for me, but now I can barely climb 10 feet up a ladder without feeling uneasy.