could of, would of, should of, you don't know until it happens,sorry guys,
Yes, you're right, even when it actually happens you'll think back and say "I should of or I could of". I can only draw on my training and experience to answer question like these.
In a perfect world we wouldn't be asking ourselves these questions, but I have been in fights, I have had a knife pulled on me and even tho I was able to disarm the attacker, I got cut first. So no one who never been in a situation like that knows exactly what they'll do, but if you train for it you will have an idea of what you'll do.
Like Danjo said the military trains and trains and until recently many soldiers never had to use what they trained for, but I would still trust them on the battle field. It's one thing to be battle tested and another to be battle ready. And that's what we train for, to be battle ready and able to adapt to a given situation.
That's why training like you would fight is so important to me.