I can 100% relate to how you're feeling.
+1 on what someone said about enlisting the services of a CBT therapist if you can afford to. Doesn't need to be forever, even 6-8 sessions can give you an insight into what's getting in the way.
I'll confess I have not read this whole thread, so am not sure if someone has already suggested this but... monster player and teacher Todd Johnson recommends a book called The Practicing Mind by Thomas M. Sterner. It's not long, and I've literally just read the first chapter but it seems to be really good at illuminating issues with the way some of us practice, and how to approach it in a more constructive way. Like focusing on the process rather than product, which is counterintuitive if we're used to chasing grades, money, recognition, etc.