Adrenaline is a hormone which increases heart rate and blood flow and prepares the body to either defend itself or to run--what is often referred to as fight or flight. Many times athletes want to trigger an adrenaline rush just before a contest to give themselves as much of an edge as possible. Frequent adrenaline rushes can be stressful to the heart.
Visualize a past situation in which you were extremely frightened. Try to relive the situation in your mind--visualize every sight, every smell and every sound that made you frightened.
Visualize a situation in the past in which you were extremely angry. The more vividly you can recall this situation the better. Let the anger flow through your body now.
Relive a stressful situation. Try to recreate the stressful feelings, recalling situations, lines of dialogue and anything else that caused you to feel as if you wanted to explode--or scream or run away.
Clench your fists and make grunting noises while forcing air through your mouth or nose in order to "get yourself psyched."