The best book on practice I’ve ever run into wasn’t even specifically about music: The Practicing Mind: Developing Focus and Discipline in Your Life Master Any Skill or Challenge by Learning to Love the Process https://www.amazon.com/dp/1608680908/ref=cm_sw_r_cp_api_i_JGGC3YXAYPD6Q1DH8E3J
Highly recommend!
If there's a book you might want to check out about this, it's probably 'The Practicing Mind' by Thomas Sterner. By learning or remembering to focus on the process instead of the outcome can help remove the anxiety about never being 'good enough' at something.
https://www.amazon.com/Practicing-Mind-Developing-Discipline-Challenge/dp/1608680908/
I am not a professional counselor, or psychologist. I'd strongly suggest seeking one out.
> It's irrational
It sounds like you already have a handle that your thoughts are irrational. That's a good start. They have less power when you see them from that vantage. Feelings are just that and they are changeable. Avoiding mirrors seems impossible. Recognizing that you are having those feelings, accepting them and moving through them and onward is what you need to practice. Another general tip for generalized anxiety is meditation. Meditation doesn't have to be 3 hours on a hill it can be 60 seconds while you are in your car. Letting you thoughts drop to zero. Thinking of nothing. I've had serious depression in the past and something that's helped me is to recognize that I'm starting a familiar thought pattern that always sends me down a multitude of other negative thoughts. The minute I feel that thought starting I meditate and think of a blank sheet of paper. It helps. I really enjoyed this book as well: http://www.amazon.com/Practicing-Mind-Developing-Discipline-Challenge/dp/1608680908/ref=sr_1_1?s=books&ie=UTF8&qid=1433686605&sr=1-1&keywords=practice+mind
Yeah, this is good stuff. Here's a couple books to really get you in that mindset:
The Practicing Mind: http://www.amazon.com/The-Practicing-Mind-Developing-Discipline/dp/1608680908
And, a classic: The Seven Habits of Highly Effective People -- particular Habit 1, and the "Circle of Concern."
Reminds me of the book The Practicing Mind
This book was a game changer for me and mindfulness.
https://www.amazon.com/Practicing-Mind-Developing-Discipline-Challenge/dp/1608680908
No need for a therapist.
http://www.hpft.nhs.uk/_uploads/documents/help-for-adults/cbt-workshop-booklet_web.pdf
CBT starts on page 7. Basically: it's not the external stimuli it's your perception of the external stimuli.
Meditation is not relaxation. It's really misunderstood by a lot of people. It's simply you practicing bringing you mind back to a blank state for a few minutes a day. After you've done this for a few weeks you start to have a lot better time controlling your thoughts. I like to think of a blank white piece of paper. We spend our entire day letting our thoughts run wild and meditation is a practice in shutting those random thoughts off.
I also highly recommend this book:
Something not directly related to producing music itself but for making music as a long term goal
http://www.amazon.ca/The-Practicing-Mind-Developing-Discipline/dp/1608680908
I think parents that force their children to practice an instrument are teaching the skill of focused practice. A very RARE skill mastered by few. It's almost like teaching meditation. Which is why meditation seems to have so much transfer when studied. Meditation is pure focus practice.
Anybody interested in this stuff should check out Sterner's The Practicing Mind. Amazing book.
https://www.amazon.com/Practicing-Mind-Developing-Discipline-Challenge/dp/1608680908