Staying calm when you feel angry is a mental game that you can master.
Being able to stay calm and assertive regardless of your emotional state protects your character, and is a huge benefit to you in all types of interpersonal communication. When you stay in control, you will not allow yourself to do or say hurtful things which you later regret. And even if someone becomes angry at you, if you stay calm, you can learn to respond appropriately and ethically even under stress.