Confidence makes a difference.

I'm a longtime player. Not claiming to be an expert, as the highest I have been is Plat V. Was Gold last season and I'm working my way up through Silver right now. That said, I've played against (and beaten) many, many Diamond and Challenger players. The big thing I notice as a primary difference? Confidence.

All too often in yolo queue I have teammates that give up too early. Usually it's about 10 minutes into the game. The major difference I see between wins and losses while behind is that better players tend to say, "I'm behind, so I'll farm and get picks when I can because I'm better than the other team and I know my champion." Silver players tend to say, "We're down a dragon and we're 2-5. The game is over." I can't tell you how many times I've won while behind early; out of about 2500 SR wins I'd say my team was behind at 20 minutes in 1000 of them.

TLDR; trust yourself and know you can win. That attitude will win you games.