Humans have the capacity to negotiate, to find out what is important to the other person and weigh that with what is important to themselves. For example, if you want my cookie and I want my cookie, we could share or find a way to get you a coookie , too. I might just say, "Sorry. I am going to eat my cookie. I can see what you want one too." I might even say, "OK I will give you my cookie."
When you are considering who gets the cookie, ask yourself, "How important is it?", "What will happen if I let go?" "What will happen if I hang on?" "Which consequences am I willing to live with?"
Anger can be destructive and harmful if it is not expressed properly. When the feeling gets so big it turns to rage, the person's mind shut off and fight or filght is the only choice. It is primal and the logical mind has been shut off. Try payign attention to things that cause anger and ask yourself the questions. See what new solutions you can come up with.