Take the up position of the basic push up and with the breath tense and relax each part of you. Go down to the bottom and repeat the drill. Lie on your back and relax and tense and relax each part. Rise to the sit up position and repeat. Lie down and lift your legs overhead and repeat. Stand up and repeat, squat to the bottom and repeat. Notice the differences in the areas that also tense up when you tense and work to relax all the parts which are not in use. This way you will be able work more efficiently and avoid freezing and slowing down when it matters.