You have measure your self worth with your failures. If you don't you can never improve and you will stay stuck where you are.
If I fail, therefore I'm worthless?
My view is slightly different. If I fail to win, or just fail to play well, I prefer to honestly review why it happened. If there are changes I can make to potentially do better next time, I'll try them. If I do not do well next time, I'll do the same again. Don't see it as an issue of self-worth at all. It appears however I'm in the minority here. Incidentally, I've already been through the self-destructive side of this equation.
Lyn