I was a life guard in high school. I did three years in the Army Military Police. At various times, I have thought that perhaps if I had wanted to go career I could have gone to one of the elite units. I recently came to the conclusion that I was wrong and it's a good thing I never tried.
I was watching a program on Special Forces combat swimmer training. These guys are already Green Berets, now they want to be bubble blowers as well. In one of the pool exercises, They go in with their tank on and a blacked out mask. An instructor disables their tank in some manner, and they are supposed to fix it by touch without surfacing. Again, this is an exercise, in a swimming pool. If they fail, they get recycled and have a chance to redo the entire program or they can just quit and not get the badge. Here's the crazy part: it is not unusual for a student to pass out under water from lack of oxygen. They will keep trying until they black out and an instructor pulls their unconscious body from the water. This is not an operation, no one will die and the mission will not fail if they surface, but these guys are so hardcore they won't even quit in the face of drowning on pride.
I have seen the difference between me and them, and I am content to remain on my side.