I found that when under pressure in a match that if I could control my breathing I could maintain better focus and not slip into a panic mode. Shorter, shallow breathing (hyperventilation) triggers the mind to panic.

So training an athlete who is fatigued, as when you have your athlete encounter many opponents in succession during training, have them focus the surroundings and control their breathing at the same time. Slower and controlled. When you can control yourself, controlling the situation becomes easier.

Not too dissimilar to high intensity interval training.

This is one way to toughen the mind.

Best of