In Chinese medicine, each organ has an emotion, much like each organ has an element associated with it. For anger, the organ association is with the Liver. I discussed some aspects of the Liver and the element of Wood in I'm a Proud Tree Hugger, so we'll be building on those concepts here. Remember that the Liver is associated with Wood. Wood likes to grow and change. Wood so much likes to grow and change that it will grow THROUGH rocks, breaking them in half. Wood will push up sidewalks. Wood is very persistent. It is very driven.
We have these same desires in ourselves. We always strive to better ourselves. We want to get things done, to get that new car, to buy that new house, to get that promotion. So what happens when our aspirations are blocked? We get angry. According to Chinese medicine, the reason we get angry is because our Wood element is unable to do something. It's frustrated.
Think back on all of the times you were angry. Didn't it all lead back to being frustrated because you were blocked? You couldn't have that toy at the store. You didn't get that promotion, but the "undeserving idiot" did. You got cut off in traffic. Interesting, don't you think?
So back to the question "When is anger useful?" Anger is useful, the same as any other emotion. As long as we don't get stuck in any one emotion - it's a part of a healthy experience. Anger (or frustration) can lead to creativity and problem solving. Think about it - some of the world's greatest inventions probably stemmed from frustrations with the current technologies!
Anger or frustration should also help us to better ourselves. The next time you find yourself cussing someone or something out, ask yourself, "Why does this bother me?" And remember that when Wood can't figure out a way to get THROUGH something, it goes AROUND.