If you feel that you're about to cross the line, just cut the communication channels for a few minutes. Not being able to hear the others can help you refocus on the game. You have a right to be annoyed, but you can also stop others from bearing the brunt of your anger.

Tilting is a biological process. Emotions hijack the brain, making it harder to think clearly. By taking three or four deep breaths, you can naturally lower your blood pressure and reoxygenate your brain. Think about the speed of your breathing and try to slow it down.

Tilting is a vicious circle where the angrier you are, the worse you play, which in turn makes you more angry. Try to be aware of the anger rising and stop it before it's too late. Taking a quick break, even for just a few minutes, can be enough to calm things down. You could also try another mod (i.e. not competitive) for a few runs.

Sometimes it's simply not the right time to play. When you've had a bad day or are having personal problems, playing in competitive mode can trigger your anger. In this case, the best solution might be to play offline, cooperatively or do something else rather than playing.