You might not believe this, but a positive attitude is really important in order to win a game.
I just had a game that we would have normally lost. The early game was pretty bad, with our entire team being behind in CS and kills.
My jungler flamed me for dying twice, one was entirely my fault, the other one was unlucky.
We almost got into an argument. I called him a 2nd class jungler and that's it.
I tried to think positive afterwards and it worked. I roamed good, killed their backline in an important teamfight, shotcalled rotations and objectives. I don't want to say that I solely carried the game, because without the peel from my "2nd class" jungler, I'd have died too often (Thank you for that).
I apologized afterwards and my jungler did too.
What I learned, what I should have known before is: Many people are tilted in the game. They tilt easily, they are tilted at the start of the game, because of recent games before.
There is nothing you can do against a tilting teammate, than playing good and ensure them to win. Even if a game seems bad, know what you have to do in order to win. Get your rotations right and focus objectives and most importantly: Do not have a negative attitude.