I think lack of fear and denial of possible repercussions is a big factor. When I was younger I remember thinking that if you have any doubt at all, (like in a stunt), you’re going to mess up, but if “know” you can do it and then just do it, it will happen the way you know it will... I think there is a real truth to that, but my problem was that I would always end up just thinking... “yeah, but what if...?” ...Plus, I think the younger you are, the better.
But then there’s Evel Knievel... I think he broke pretty much every bone in his body... maybe he always had last second doubts during each stunt.😬