STAYING CALM IN A FIGHT
The ability to remain calm in a real situation can be very difficult indeed. It almost seems like a contradiction. It sounds very strange to relax while you're trying to hit someone and avoid being hit, but you must do this. One of the keys to doing this is learning to control your breath. This is done through Qigong breathing exercises. If you practice these exercises regularly, it will have tremendous benefit to your overall health and the ability to remain calm.
RELAXATION, AWARENESS, INTENT are the keys to combat. You must stay relaxed inn order to be properly aware and you must have intent to actually hurt the opponent. But above all that, it's imperative simpyl for overall health. Less tension means less neck, shoulder, and back pain, along with less stress.