Aside from keeping your wits about you, there are few more important things than strength and stamina in a life-or-death situation. (Or even just when you don’t want to look like a mouth-breather in front of your friends—that’s arguably every bit as crucial.)
Whether you are a shooter, a fighter, or a hobbyist, your lungs are your real “first-line” weapon. Even if you are unarmed when you encounter a life-threatening situation, those lungs and that stamina will at the very least get you out of harm’s way, to fight another day.
It’s difficult to fully convey what happens to your body during a gunfight, but combat is hands-down the most physically demanding thing a human being can endure, besides curling. It is a test of everything you are made of. And the weak—guess what?—don’t inherit shit. They die, in a sorry, dirty, crumpled mess at the business end of a thunder stick, at the hands of the man who trained and fought harder than they did.