How do people not freak out when doing stunts?

Question

like being in a really small box or being covered in snakes like fear factor stuff.

Answer 1

Its a matter of being scared or not. You could stuff me in a small box or cover me with snakes just fine, but put me on a tight rope and ill be done in a few seconds

Answer 2

You pick something that doesn't terrify you and you practise doing it safely a lot. Many stunts look more dangerous than they really are. Once you can do the stunt easily you then add some showmanship and do it in front of an audience.

Answer 3

Some people just lack fear of anything, either because they are rational and know it's safe, or because they could care less about what happens to them.