I don't want to be toxic anymore
Then don't be. It sounds like a smartass comment, but it's not. Literally, you have all of the control in this situation. You're allowing yourself to be a helpless victim. Take control back.
There are just some things about this game that you have to accept if you're going to play it. You have no control over whether someone on your team craps the bed and starts smearing it all over the Rift. You DO, however, have control over how you react to that situation. You don't have to start raging out like a chimp on steroids, and you don't have to have a mental breakdown. Give it it's proper place in your life and let it go.
I know those kind of people are annoying, and it's not fun when you end up in a lobby that turns into a clusterfuck, but it's the nature of playing the game. It happens, because you're not playing with computers, you're playing with people. Random, unpredictable, flawed people. None of whom are holding a gun to your head and telling you that you have to react a certain specific way to their clown shoe bullshit.
The best tip is just focus on yourself and how you're playing. It doesn't matter if your teammates are all brain dead, or making 1000 IQ plays every 10 seconds - your focus is on you. Sure, maybe if your jungler had ganked at that very second, you might have lived, but you also may have lived if you hadn't over-extended. Instead of cursing the jungler for not compensating for your mistake, make your focus not making that mistake. Instead of cursing top lane for feeding their opponent, focus more on how you're going to starve your opponent.
When you run into players that are pushing your buttons...don't let them push your buttons. Maybe they're new and dumb and learning. Maybe they're screwing around to piss people off. It doesn't matter. Just let it go.
Taking regular breaks is important with this game, even after wins. Playing matches back to back to back will grind on anyone. Get up...walk around...clear up whatever thoughts you have about the last match. Do whatever you have to so you're going into your next match with as clean of a slate as possible. Also, if they really are trolling, you're less likely to get matched up with them again if you wait to queue up for your next match.
This is not a relaxing game, and it's not a game to try to relax to. It's a competitive game that requires you to process large amounts of information on a second-by-second basis for over 20 minutes a match. That sort of thing is mentally taxing. Take that into consideration too. Only try to play this game when you're in the proper state of mind to play this game.
In the end, it's all up to you.