Generating Self Belief
All my life I heard the advice - 'believe in yourself'. It Makes sense. You don't need to sell it. All the greats believed in themselves, even to the point of delusion. You require self-belief to do anything worthwhile.
It is easy to believe in yourself if it is easy or part of your persona. Someone used to doing well academically can have setbacks but won't lose the belief that they can do well again. They are 'smart'. It is a core belief.
But doing something new and hard. Something antagonistic to your persona. That is where you need to generate that self-belief. Writing fiction is that thing for me. I always classified myself as the 'non-creative' type. For most of my life, I had resigned myself to being a reader. An admirer of art rather than the artist. Something I decided to change.
The best way to generate self believe in my opinion is to take action. Just do the thing and do it consistently. And if you can't do the whole thing do a miniature version. So I started writing. Novel outlines. Short stories. A few chapters here and there. Slowly and then all of a sudden my sense of belief rose.
I also made sure that my goals were process-based and not outcome-based. The goal was to write consistently and create something I am proud of. You don't need someone to motivate you or need visualization hijinks to believe in yourself. You don't have to wonder if you can do something when you are doing it. Just do the thing.