I hope your new diagnosis helps you. Learning more about how you think, what motivates you, and what holds you back can help a lot with choosing realistic and satisfying goals. If you keep at it, I think you'll figure out how to achieve something you can call success.

And for what it's worth, I don't think it's possible to be a failure, but I do understand the pain of defeat. Thinking more about it, defeat seems like the pain of wanting something, believing (correctly or otherwise) that it's impossible, and then continuing to hold onto that desire. It's the gap between what we believe to be possible and our expectations, not all that different from grief.