It depends on where you are in terms of the professional help you can get.
may help you to calm yourself so that you are not so sensitive/emotional to events that are disturbing you (like your friend's affecting you)
Mindfulness sessions help by changing the way you think/react emotionally to events/people/relations/happenings in the world.
or Aggression control courses help you to change your behaviour in many ways for ex channelling your emotions constructively etc
CBT (cognitive behaviour therapy
) can help you by making you think about your thoughts, feelings, actions an their interrelationships
Hobbies like music or physical exercises like cycling help you feel happy in yourselves there by diverting your anger
Breathing techniques help you by stopping you from acting on the intensse surge of emotion/anger that you feel when faced with events, thus stopping you from "behaving" or acting on emotions at their height and giving you time to think clearly.
Try and choose depending on what helps you or what is available.