Anger is a powerful emotion that everyone experiences. Anger is completley normal and healthy. It's when anger gets out of control and turns destructive it can lead to problems.
Anger can be caused by both internal and external events. You can be angry at a specific person or an event. The instinctive, naurtal way to express anger is to respond aggressively. Anger inspires powerful, ofter very aggressive feelings, thoughts and behaivors, which allows us to fight and defend when we are attcked. Therefore, a certain amount of anger is necassary for survival.
Be an example. You never know who's looking up to you. What little girl wants to be just like you and will mimic your actions. Forgive and forget. Dont dwell on the little things. It is easier to forget then to drag it out and let it become a huge issue.
You have to learn to forget the small things, and what other people say. Concentrate on you. If you spend your time focusing on what other people do, that gives you no time to enjoy your life. Remember high shcool isnt forever. In a few months this petty high school drama wont even cross your mind.
Your always going to run into people that make you angry and you cant change that. You can change how you react to them. Its normal to get defensive when someone critisizes you. But you need to give yourself time to think about it and not let it your anger get out of control.