Let the body move, do not think about the body and let your mind focus on one point. Your Hara or center (below the naval).

If you move with tense muscles, you will lose any strength contest. Instead, relax and align your bone structure so you use the minimal amount of muscles needed to move.

Now apply this to gaming: if you are tense, your reaction time will slow down. So relax, breathe and tap lightly upon the keys.

Aikido [en.wikipedia.org]
Systema [en.wikipedia.org]
Martial Qi-Gong [en.wikipedia.org]