Now that I’ve read the rest of this thread, I agree with
@Bigmurph : Having gone through crisis and having had the responsibility of resolving or leading its resolution teaches the brain to live with strife, to not freak out when the adrenaline rush hits, to keep a cool head, ignore the fear as much as possible, and just do what you need to do to resolve the situation. Classic military and rescue training and experience. The people who have been through that are best prepared to handle future crisis of any type. Mental toughness is a learned response. Comes more naturally to some than others.
For me (poor comparison, I know), it’s getting up in Court in front of a room full of people scrutinizing every word you say, every gesture you make, every hair on your head or your face, your clothes, how articulate you are, how charming you are, and so on. And you have to put all of that out of your head and do what you need to do to win because that is what the client is paying you to do. At the beginning, the adrenaline rush is intense, and you have to squelch it or you’ll fuck up. The more you do it, the better you get. But the fear and the adrenaline never goes away. You just get better at handling it.
Again, a very poor comparison to the life-threatening situations you guys see in the military and rescue business.