Like anything, you need to practice training yourself at handling anger.
When my kids get angry, I teach them to ask questions. "Why?!!" "Why didn't they let me play with them?" "Why does my sister always get to use my toys?!" "Why does it make me feel this way?!" "What can I do to prevent this in the future?!"
The most understanding you can gain during a confrontation, the better you train your mind to react in that way rather than in our following our instincts. We are, by default, animals, and anger is part of our fight-flight response - but it's something we can reprogram with practice. ...especially if you start with a young malleable mind.