So hear me out, I had a bit of an epiphany recently and I'd like to try and explain it even though it seems convoluted. 

When I was a kid playing board games with older siblings, my oldest brother was a really sore loser. He constantly accused people of cheating when they didn't. Especially my other brother, he got the worst of it.

It was then that I taught myself how not to win, because not winning was preferable to being called a cheater.

I don't know how to remedy this patterning so late in the game.

Any advice?

You can try meditation 
Also there's this book "the mountain is you" that I think can really help