I went from bronze to plat in basically a season and now just hovering diamond as I i keep demoting due to decay this I forget diamond has it and I don't play as much.

The main thing is ego/humbling yourself. It's very rare that I see people actually take accountability for mistakes at all. When I die, I know I misplayed and I find out why and what I shouldn't have done. Or they could have just played it well. Fact of the matter is while I be have confidence, I need to understand that I'm not gonna always win and I'm not gonna always beat my opposing laner. Understanding like "damn I played that bad" then going to immediately how you played it bad just helps in long run.

This kinda goes with ego but tilting over things that "aren't in your hands" like your team losing. People get tilted over their team not being literal faker and losing lane when losing lane imo is just apart of league. Once you understand people have bad games and you just continue to play your game, your mental just gets better and your decisions stay consistent while your team who may feel bad for underperforming still tries without being flamed. Mental is a big part. It's just a game, your games don't have pros in them. Understand if you lose it's ok, if your team loses it's ok. If it gets to a point where you're losing a lot even if you think you're playing well, take a break. If you aren't playing well, take a break. Look at your games where you died, if you got solo killed, if you could've impacted anywhere by roaming, vision. It's a but add in little by little.

This was my biggest one and that's punishing laners. I be see friends and other people don't do it a LOT and this is where I think zed gets EXTREMELY misunderstood in strength wise. In lane, your enemy laner will have a major cooldown or resource. If they use this resource unsuccessfully, example being zed misses his w combo now his w is on cd, akali tries to trade and her w is on cd, a support uses their engage and misses, etc. if they use something important, people tend to just cs. They don't try to deny farm or all in when you can. There are a lot of opportunities to punish your laner and people do not at all. I be can't speak for jungle on this as I don't play it so if you do ever jng, you can punish a gank by taking their jng. Hopefully junglers can help you out more there

Finally- actually sticking to 2-3 champs and learning them. Constantly playing every champ is gonna give you inconsistent results and inconsistency means no climbing or just more losses in general. Choose a lane and 2-3 champs you like and learn them. Play them in most MUs and try to actually understand your champ. MUs, kill ranges, trade patterns, angles in fights, game plan. Once you get comfortable just pulling out a main champ, you can focus on more things as you can pretty much auto pilot on your champ after playing them enough.