If you want to feel more confidence, decide more things.
I have a special skill as a pianist - I am a highly effective sight-reader. What does that mean? A singer/artist can put a piece of music in front of me and I can quickly understand what needs to be done and render a performance (at sight - without preparation) as if I've played the piece my entire life. There pianists who exercise that skill much better than I, but I am particularly good at it.
That skill is not an innate skill - it needs to be practiced... and practiced in a specific way.
Like learning to ride a bike, the only way you get better at sight reading is by sight reading; and doing it under pressure.
You need to train your mind to do four things:
Consume and make sense of an enormous amount of information;
Relate what needs to be done to what you can do; and finally,
Decide what you will do and accept the outcome (good or bad) in advance.
Reflect on what you could do better next time, and move on.
Building self-confidence is no different.Understand what needs to be done to the best of your ability.
Relate what needs to be done to what you know how to do.
Decide what you will do, accept the outcome in advance, and do it.
Reflect on what worked, what didn't, and commit to doing better next time.
The work of the artist is the work of creating, and creating is deciding.
To be more confident in you and your art: create more decisions, learn, and do it again.
Just like learning how to ride a bicycle.