How do I stop being paranoid?

I think you are being paranoid about it because if you're good and one day you say you hope you don't become bad and then suddenly you think you have doesn't really mean you're bad at water polo. It's just you seeing yourself that way because you think of it like that. Just practice a bit more if you think you're not good enough anymore.. its good to set higher standards.. and hey.. that might be what you did. You can't jinx yourself.. just remember that. Practice harder and try your best...cuz that's all you can do.. don't expect yourself to be superly good.. just try your best and stuff and you should be happy with yourself cuz there was nothing more you could do.