Is easy enough to come by merely by being abjectly stupid.
In actuality I would say that your average "extreme" athlete knows just how dangerous what they are doing is, they just fail to care. Even considering that, most extreme sports aren't even that dangerous, overall, because the participants know what they're doing.
Sure, trying to pull a 720 on a half-pipe with a skateboard is suicidal for you or I, however since Tony Hawk has been skating forever and a day, then he has a fairly safe chance of pulling it off. Same goes for sky diving, snow boarding, BMXing, etc.
Its just that we never see the baby steps all of these athletes take when learning their sport, but instead just the fantastic results they achieve after years of practice.
"Too much wasabi and you'll be crying like you did at the last ten minutes of The Terminator" - Alton Brown