Playing competitive games easily causes emotional fluctuations, such as anger triggered by “useless teammates” or frustration from being repeatedly beaten by a skilled player (sometimes they even taunt you, which is awful). This is a great opportunity to practice controlling your emotions.
Whenever I experience emotional fluctuations, the phrase “quit the emotion” helps me quickly regain calm; you can try it too.
PS: You can also use games to train patience, for example by flying a bomber in War Thunder. Bombers can’t match fighters in speed or climb rate, but you have to fly higher than the fighters to stay safe.