Self doubt: Create certainty instead? Or act despite self-doubt?

I recently got coached on my self-doubt. I was overthinking to create certainty, which wasn’t working. The coach pointed out that no amount of thinking and strategy can create certainty. Doubt, or certainty, are created by my mind, my thinking. I agree.
But I have this question: Brooke talks about self-doubt arising often when we try something new, when we set a big goal, and so on. Self-doubt is a good sign, means that we are stretching ourselves, and we can act in the direction of our goal despite it.
But if I can create certainty with my mind, why bother keeping the self-doubt? Why not just decide to think “This is the exact next step I need to take” or ” I am perfect for this job”… instead of thinking “I am unsure but I’ll take this step anyway” or “I am not perfect yet for the job but I will learn on the job…”
I think personally I prefer choosing thoughts that create certainty, rather than act despite self-doubt, because I know that action driven by self-doubt, or action taken whilst ‘ignoring’ or ‘overriding’ self-doubt, won’t be as effective…
Can you clarify please?