I guess this is ultimately what I'm saying to low ELO players, and it can be broken down into a couple of things:
Your teams mistakes are not connected to your own, in that you don't get to make mistakes just because your teammates do. When you flash in and you see Amumu didn't hit his Ultimate, you shouldn't be like "OMFG THIS MUMU SUCKS" and defend your own death. Your death was a mistake, irrelevant to his. You're not going to get better as a player by fixing other peoples mistakes.
Not every game in Solo Queue is winnable, but that puts more emphasis on you having to win every game that is. There are variables outside of your control AT TIMES, but you still need to do your best to win every game and not hit the concede button. Even if it's 21 to 7. When you're having games where the score is 11 to 7, and they have 11, and you're 7-1, it's annoying. But it's winnable. You just need to play near perfectly. Like yeah it sucks that you don't get to make mistakes anymore that game like your team does, but that's how it goes when you try to win the winnable games.
Avoid typing. You calling something dumb, bad, or wrong makes things worse. Communicate mostly by pings, and don't do something just because you want to. Like if you want dragon, and your team isn't coming, you can't go there, die to them when trying to steal, then go WTF TEAM THATS A FREE DRAGON. Ignore trolls. Turn of all chat if you need to.
If you are a lower ELO player, especially the very low players like Bronze, you are very bad at league of legends. It's not your champion pool, your rune page, or the shitty teammates you have, it's you. But good news: you can improve literally everything you do. Which is awesome, because it means you can grow way way faster. It also means the people you play with and against are equally as bad. Ever thrown a won game? Probably. That means your opponent will probably throw too if you let them.
Don't give up. Your mentality alone is the reason you'll climb, or the reason you'll tilt and lose winnable games. One of the most valuable things you can learn to do in League is learn how to play from behind. You're not going to be up 6 to 1 every game. Sometimes you'll be down 8-0. You need to learn how to win those games. If you've got one foot out the door and you're upset and you're not putting full effort into those games, you'll never learn how to win from behind, and that's an easy 30% more losses.
I swear, it's everywhere, but Bronze players especially have an insane external locust of control. I watched my friend Smurf today. He's the guy who teaches me, he's diamond. He gets on someones Bronze 2 account, and won all 8 of his games, usually with Quadra kills and absurd scores. In one game, the dummies he was playing against Dove him at level 1 middle, and he had 3 kills before laning phase even started. I was in tears laughing. But that's not the point. The point is: I heard every excuse under the sun for why their team lost to him, other than "Man I got outplayed, I'm not very good." Sooo many excuses. "WTF do you have a lag switch?!!?", "Wow I can't carry this Maokai", "WTF This is the 8th time I've lost PROMOS due to this teammates :C", "Zed is an overpowered champion, that's why I don't play him. I hate being OP".
The coolest and happiest thing I learned is that I'm god awful at league of legends. Every game, I count hundreds of mistakes I make. I smile LITERALLY immediately as I find out how dumb I am for doing x instead of y. It means I can get better. That's the best feeling in the world, knowing that you can get better and doing something different than you did before. Accept that you're bad, learn from yourself, avoid all this finger pointing, and you WILL get so much better so much faster.
/rant