Answer: When you feel your anger building up, tighten all your muscles; then let go all at once.

This  quick muscle-relaxation technique is mentioned in Daniel Goleman’s book Working with Emotional Intelligence (p 273).

Try it now. Pretend you are starting to feel angry about something. Tighten all your muscles as hard as you can.  Hold. Then let go. No more anger!

Practice this a couple of times a day for the next few days so you’ll remember what to do next time you get angry.