Discipline and ability to take pain is a very important part of SF. When we are out there we migh be 100 km away from closest friendly force. There is a chance that you not going to get airlift to the closest field hospital is ya get wound anytime soon, and in the case of most minor wound you a expected to keep on fighting and at 110%, cos they need every man they have.
Discipline, training, specialize skill, durable and endurance it what get a SF ready for actual combat. Actual combat is where you gian experience. Your experience is as important as your training but your discipline is your most important thing.