"Don't even for one second consider yourself good, ever....This is the easiest way to cause yourself to stay your current elo, if you always think you're good then you end up blaming your team mates and never owning up to yours mistakes. There is always new stuff to learn and things to improve on, that's why I find humble LCS players tend to improve the fastest."
Don't consider yourself good?....that's the stupidest tip I've ever heard. League's ELO has been proven to be based mostly on luck rather than skill. The luck is getting paired with compatible teammates. The skill is secondary. Yeah, not being toxic always helps because all that does is make enemies out of your teammates. But that simply has to do with actually being a 'good' player in general...not a successful one in elo...