Well, the higher up you are, the smaller the distance looks horizontally to where you want to jump to down below. I'm sure that mistake in perspective has caused the untimely demise of more than one person.
Yeah, I look back on things I did as a kid too, and wonder how I survived it all. Heck, I used to body surf all of the time in Ocean City and didn't realize how many people get broken necks that way.