Rage in MMO games?

Now I have short nerves and I try to keep calm as possible it is at the moment. My last game was with Riven on top, but in queue i was 2nd pick and i wanted to go Fiora jungle and wrote in chat "Don't ban Fiora" and then he said "u won go jungl fiora go tenk" and he banned Fiora. I was so furious I started to verbally harass him in chat. Then I calmed down a bit ant took Riven top. I was playing against Nasus and it was all fine unling their jungler(yi) started ganking first 2 times I managed to escape, but 3rd and 4th time I couldn't do anything and my jungle didn't gank at all in whole 30 min game he wasn't one single time on top and their jugler was around 6-7 times. I was so furious started spamming cancer, die die die and etc. So guys how do you prevent these situations from happening?