A strategy that has given me some success in my ranked games.

Whenever I go into a ranked game, I disable game music and put on some music from YouTube or SoundCloud. But it's not just any music, it's extremely chill and calm music. But why? Think about it this way. Whenever you are using the game's music and you loose, it creates a negative association in your brain. If you go on a losing streak, your brain associates "League of Legends music" with "losing." This will make you not feel as good when you hear the music, and thus you will tilt faster. By putting on an external source of music that you can rotate at will, you don't allow these connotations to have such an effect. Also, the music that you put on should be extremely calm. If you use energetic music, it makes your blood pump and invokes violence and movement. League of Legends is a game about strategy, not reflexes, so you want to be calm in order to think more clearly.

TL;DR putting on chill music can stop you from tilting and make you play better.