At OP's level (1800 lichess), there are only two rules of importance: "don't blunder" and "don't give up." Here's one of their recent wins [1]: in this game, OP had black and was completely lost, down a rook and a knight. Black played on, white dropped their guard and blundered, black pounced on it, and black gets the full point, having made the second-to-last mistake.

I am 2100 in lichess 5/0. Most of my games are still resolved by blunders on either side. It's rare to get a positional advantage and then grind away; instead someone didn't see that backwards knight or lateral queen move.

1: https://lichess.org/fhnTl1lE/black#72