If you lose a game it means that you did not find a way to carry hard enough.

Figure out how to carry harder.

Some games that is going to mean stomping your lane opponent and drawing pressure to you.

Some games that is going to mean stomping your lane opponent and then transferring you lead to the rest of the map.

Some games that is going to mean neutralizing at least one player on the enemy team even if you don't make splashy plays.

Some games that is going to mean playing in a way that allows you to absorb jungle pressure without dying.

Some games that is going to mean transitioning from a diver to a peeler.

Some games that is going to mean cheer leading for a team that is down.

Some games that is going to mean losing as slowly as possible until the enemy team makes a major mistake out of impatience.

Sometimes that means revamping your champion pool to one that can thrive in the current META.

Sometimes that might mean reviewing your replays to understand why you died.

Sometimes that might mean seeking out coaching for an outside set of eyes and ideas on what you can do to improve.

It is not that your team and their play doesn't matter.

It is just the fact that you will be playing with different teammates every game (until very high ELO).

So the only point of consistency between games is your own play.

You have to know what you need to do to carry a game through out all stages of the game.

And then exectue on those things consistently.