My son is taking aikido, and at the end of lessons they play games such as chicken, or knock over the Sensei. The kids are kids, under age 10, and Sensei is an adult. In chicken, you must hop around holding one foot up, while holding the hand of Sensei (or another opponent) in your hand, and the goal is to knock the other person down. It’s similar in the other game, except you must stand facing each other, and not move your feet as you attempt to knock the other person down.
My son, age 9, is pretty good at the game, and may be the only person who can beat Sensei. His strategy, he says, is to let the other boys tire Sensei out, and then he plays patiently, using as little energy as possible, until he senses an opening and can claim victory. The thing is, he talks about the adrenaline rush he gets when it is his turn to play, and how he gets all shaky after the game is over.
It seems like he is using the adrenaline to his advantage in this situation. There must be some mental mechanism that can turn it on and off. From what @darthbush said, it sounds like it not only focuses the vision, but also the mind. I don’t know if he likes the feeling or its aftermath, but it does seem like he consciously uses it as best he can.
I find that I can achieve a similar state of focus and energy, where I can do things that I can’t do, when I go deep inside; my brain stops thinking in words, and I am barely aware of what I am doing. If I am dancing, I can leap higher than I could in normal consciousness, or do things with precision and grace that I do not usually have. If playing music, I am just heightened. The nice thing about this is that I don’t get the jitters afterwords, at least, not much. I also get that adrenaline feeling when I’m facing a crowd, and I have to say something. If I’m asking a question, I am usually so hopped up that I can’t hear the answer. Still, in my line of work, it is more important to ask good questions than it is to instantly understand the answer.