Here are a few things I use to ease me.
- Scream at the screen instead
- Understand that 40% of the games you'll stomp, 40% of the games you'll get stomped, 20% of the games you have control over with your decision making & communication. You want to influence those 20%s, not rage over the 40% which you won't have control over.
- Flick your enter key out, so you can't type
- /mute people whom flame you. If you don't want to do that due to communication reasons, learn to ignore everything that you deem as negative.
- Dynamic queue with a few people of similar skill / attitudes and get you out of the "ELO hell" first.
- Don't expect them to perform, if they do, you should be surprised instead. Think that they are where they belong cos of what they know and what they do.
- provide good constructive feedback with solid reasoning as criticism. You have more ingame knowledge, so be nice about it as they probably don't know why certain things are good in different scenarios. But then again, they are where they belong, so assume they won't change.
- Acknowledge lost games and try different things out, maybe a different build to see if you can turn things around or just a different minigame all together.
I had a Jg Mundo forgetting smite, and he rushed frozen mallet first item. Died 3 times to jungle camps and would blame our most fed Varus for going 9/7/3, but 7 times is too much to die (yea, if you were able to jungle properly and keep enemy shaco in check, maybe that 7 times wouldn't have been there). He only started building a sunfire after I told him that it helps with his clears. I even won the lane and my ADC was 80 CS > their adc.
Then again, here is where I think to myself that this is one of the 40% games where I can't have any influence over. Was Mundo trolling? no, he was just bad and belongs in bronze 5 with the decisions he made. So I acknowledge that the game is probably a lost cause and start playing the "guess where the enemy is" game.
This is basically mentally guessing where every enemy is at any specific points of the game. Then using blue trinket / wards to reveal them and see how good my guesses were.
You can also start practicing your skill shots (I've seen pros dark binding enemies through minions, eventually I want to be able to do that XD), getting more used to the travel speed of the missles etc etc or even zoning ranges.
Maybe predict how people will react to certain movements (aka zoning practice) and use that lost game as a method to improve other mechanical plays.