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.