>>717628905 (OP)
Nothing wrong with not being able to find joy in defeat, it's nothing but a reminder that you still have a ways to go and that there's someone better than you out there.
The issue comes when the final mark of win or loss matters to you so much that you can't find any enjoyment in a fight unless you come out of it with a win. So I wouldn't say that you need to learn how to find joy in defeat, but rather that you need to learn how to have fun in fights that you end up losing in the end, that sting of losing does lose a lot of it's pain if you can recall those moments that released the good feel chemicals in your brain.
Now if you got completely washed, then that's another story, just try to burn that match from memory and move on. And if all else fails, remember that it's just a video game and nobody will ever care about your w/l record more than yourself.