<human>: Can you condense the text into three sentences or less?

Sorry for the convoluted title and double apology if this isn't the right place to post this, but I didn't know where to post.

Basically, my girlfriend of 6 months competes for her University in a team sport (doesn't matter which one), and she really lets her performance affect her. If she doesn't do well, she gets REALLY down about it and jumps to really harsh conclusions e.g. "My team is going to fail because of me!".

I know that it is mostly her attitude that forces her to fold under pressure and even stops her from getting better (i.e. the old "Why should I bother practicing if I'm not as good as I used to be"), but I'm having a hard time getting through to her.

I'm definitely not trying to educate her about practicing or discipline and am really focusing on improving her outlook and developing a Positive Mental Attitude (yikes), but I think she kind of ignores me because she knows I love her unconditionally and that I know zero about sports.

My question is; are there any resources I can gently guide her towards, aside from being loving and supportive? We have the kind of relationship where I could give her a book about "keeping your head in the game" or "focusing on the positive" and it would make a big impact. I know this would mean a lot to her and I'm struggling to find the right next step. Many thanks in advance!
<bot>: My gf gets bummed out when doesn't sport well and it stops her from getting better and GREATLY affects her self-worth.