Do your ****ing job
I'm tired of seeing people brag about carrying and bitch at their team when their carry doesn't win the game. You're carrying because the rest of your team is doing poorly. Statistically, if your team were doing as well as you, you wouldn't be carrying. If everyone carries, no one carries, and that's the problem. Being the type who brags about carrying is literally benefiting from your team's poor performance, and you wonder why you can't carry games consistently.
You know what would help? If you did your job. Or rather, if you'd re-evaluate what your job actually is. Your job is to play to your weakest teammate's strengths. One gorged wolf does not a fed pack make. One strong set of jaws does not defend the territory. Your purpose is not to carry your team, it's to help your team win.
Winning means more than having the highest score. So you have 38 kills. Unfortunately, the prey is the nexus, not the champions. Those 38 kills mean nothing if your ceaseless quest to pick off isolated champions keeps you away from teamfights, gets your team wiped, and eventually tears your nexus down. Did you know a team can win a game without having a single kill? It's tricky, but it's absolutely possible.
To that end, if you're not willing to find out who your weakest link is and help him succeed despite his shortcomings, you're going to lose more often than you win. It's basic science. A single frail hair is easily snapped, but try to snap all the hairs on a horse's tail and you'll fail every time.