In a close match, the player who controls their temper usually controls the score.

When the margin is narrow, mistakes decide the result, and temper is what manufactures mistakes. Anger narrows your attention onto the last unfair thing instead of the next decision, which is exactly the wrong focus while everything is close. Staying level is less about being calm by nature than about staying able to think.

Work out your own tell: the clenched jaw, the faster speech, the urge to say something. When it appears, take one slow breath and name your next action to yourself. That small gap is usually enough to get you back to playing.