There are several causes of anger in human. I think the cause might be the action of his/her own self, as the thing one is done or said is not satisfied by one own self. In this case the unbalanced behavior (nature versus nurtured) cause tension which is a root cause of anger. It's safe to say that people with more tension and being anxious is more prone to getting anger.
Here are three factors that I think usually cause tension:
1. Situation
The reason why people have tension or be anxious is because they don't satisfy with the situation that randomly take place during their life. In some situation when people become an angry jerk, they will try to stay in their comfort zone and thus avoid that situation by escaping physically or mentally to some other places. In this case, the cause of anger is people's urge to control the situation. The unwanted situation cause mental pain especially when thing doesn't happen just the way they expected.
2. Behavior of other people
In most cases, angry jerk show how angry they are by throwing their anger to people around them which seemingly be the cause of anger. However, a certain person could partly cause anger in another person but not being the root cause of it. Again, we might say that if the action of one person is a root cause of another person's anger, avoiding that person will cut down anger. In fact, the root cause of anger is the urge to control the behavior of other people. And, we could say that behavior of other people cause the anger of one person if that person wanted to control the behavior of other people.
People who get angry because of the above outside factors would have a lot of interpersonal problems. They're actually get angry because of their expectation in other people or situation. In addition to these outside factors and as mentioned above, one can also get angry for their own misbehavior which they don't actually expected to have from themselves.
3. Own behavior
Sometimes, the cause of anger is because a person want to control their own behavior. What they do is believe in perfectionism and set perfect standard for their own behavior. In this case they get angry with themselves because they didn't happy with what they have done or said and their feeling of regret would cause them to be a moody person. At that time, they struggle themselves with rumination and intrapersonal problems within themselves.
Therefore, anger has something to do with the urge to control the situation and/or people's behavior (including their own). So, when you stop controlling the situation or people, there is nothing to get angry with. People should also accept everything that mean to happen and let the situation flow as it should be. If they try to see the imperfection of situation and people they will be away from the idea of perfectionist who expect perfection in everything. My advice is accept yourself for who you're really are, love yourself and understand other people and their situation.
