I think that the wax and wane of confidence is a natural (and healthy) cycle to preserve.

You start knowing nothing, and have no confidence, then learn stuff and your confidence builds, then you capitalize on that (learning x confidence) by doing productive things, then you hit barriers that create confusion and break down your confidence, at which point you realize you knew nothing and start learning like a beginner again.

Unhealthy confidence does not have this pattern, whether it's low or high. Even "medium" confidence, IMO, signals some kind of rut that one is stuck in, which tends to stifle creativity.

This is a good comment explains why discussions so often are so painful.

I quite often get explained to me the things I already know, in long monologues. Even things that I have created, only having people explain them to me years later, but using terms somewhat incorrectly etc.

And then I'm probably also doing that to other people.

This is very encouraging! As I said in another comment, lack of confidence in opinions due to realizing the limits of knowledge feels debilitating. Glad to hear maybe it’s just the start of learning like a beginner again!