The Parable of the Empty Boat. A monk decides to meditate alone, away from his monastery.
He takes his boat out to the middle of the lake, moors it there, closes his eyes, and begins his meditation. After a few hours of undisturbed silence, he suddenly feels the bump of another boat colliding with his own.
With his eyes still closed, he senses anger bubbling up.
By the time he opens his eyes, he is ready to scream at the boatman who dared disturb his meditation. But when looks, he sees that the boat is empty! It had probably got untethered and floated to the middle of the lake.
At that moment, the monk achieves Self-Realization, and understands that the anger he so righteously feels, is within him. It merely needs the bump of an external object to provoke it out of him. From then on, whenever he comes across someone who irritates him or provokes him to anger, he reminds himself, “This person is merely an empty boat. It's not what's making me angry - the anger is already within me. If I didn't have anger, it wouldn't come out". And then chooses how to respond instead.

Not reacting angrily doesn't mean you don't care about something, sometimes it means you care enough about yourself to walk away. This isn't to say you should never get angry - anger is a part of the human experience and tells you what's important to you.
What I'm saying is, use your anger in positive ways. Channel it in ways that you can both, express it safely and let it fuel your power and determination to create a life and experiences that move you forward. And remember what a wise person once said - anger is like drinking poison and expecting the other person to die. I think most of us have to work on this..