I still do buuuut...
First off. You are playing competitive games. Remember this.
Here is a fun fact, most people aren't very good at pvp games. Here is the worst part. Most people think they are good at pvp games. See the problem? You get mad because you don't like to lose. Nobody likes to lose, but you need to look at losing as learning how to get better.
If you find an excuse or blame something exterior to yourself for losing, then you will never get better. This anger you feel is believing you are good and getting frustrated when you lose.
If you step back, and accept. the fact that there will always be someone better than you, you won't take it so personally. Use each loss to figure out what you could have done differently to get a different outcome. That is how the good players become great, the opposite is how the good players just become angry.