To feel confident, just do what you resolve to do.
Do that every day to build on the previous day’s success and confidence.
Start with small tasks, and move to bigger ones.
Increase the difficulty often.
Ok, to fail at times. Your confidence buffer will help deal with it.
There are other ways to feel confident, too, like planning well, thinking things through, connecting with, and getting the backing of the right people.
But nothing beats taking action.
So when you feel stuck and low on confidence, just do what needs to be done first thing in the day, and do that consistently, and things will start to fall in place.