Ok, you know when you were suddenly winning (e.g. winning material EXCEPT MATE), then you got too overconfident? Well, here’s the mistake, you got overconfident when you’re winning and then started singing “opponent is trash! x3” or whatever.
But being overconfident turns deflects your attention on the game away, then you started blundering pieces or getting mated.
How to fix this?
It’s simple, do not get too happy when you were winning, try to stay calm until you’ve won the game.
This is about your emotions that affects your game.