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

I think now that you have discovered the pattern and are aware of it, you've gone half of the way 
Which is great!

In order to play, first of all, one must have the capacity, that is, one must be able to tolerate winning and losing the game, and in case of failure, one should not accuse someone of cheating and enter the game with sufficient skill.