Anything you can do to keep your mind in the present moment helps. I think most, if not all of the problems we have with not performing our best under stress are due to the anticipation of something, usually something bad, that might happen in the very near future. Even the anticipation of something favorable is not helpful, because we can't hit anything in the future, only in the present moment. They say that visualization helps, but I think that means long term visualization of the path you would like your life to take, not visualizing an arrow sticking out of a deer while it is still sitting in your bow. The only thing that is helpful in that moment is focusing on the specific steps that need to happen to shoot the arrow correctly, as they are happening.
I think I’ve made the mistake at times of wanting a stressful experience, like shooting a buck or shooting a winning shot in a tournament, to be the same as shooting a shot when I'm wandering around the course with my dog, where I can shoot as well as I’m capable of shooting without thinking about anything. Maybe some people can make their minds a complete blank in stressful situations, but I certainly can't. If I try to make my mind all peaceful and blank in a stressful situation, it's just an invitation for all kinds of stressful anticipatory thoughts to rush in. The only thing I have found to be successful is Joel Turner's method of focusing on exactly what I’m doing loudly enough to override all the distructive thoughts that might otherwise fill up that space.