Reaction v. Response
There is a big difference between reaction and response.
Reaction is driven by the other person. He insults you, you get upset, and out of anger comes your action. You are no longer an independent person. Anyone can pull you into one direction or the other.
Response arrives from freedom because it is not dependent on the other person. He insults you, but you dont become angry. Instead, you think deeply on why he insulted you. Maybe he was right. In which case you should thank him and not get angry. Or maybe he was wrong. If he was wrong then why should you destroy your mood for something incorrect?
During the moment, go backwards to the source and you'll realize that there is actually no anger at all.