With enough confidence can one communicate generic confidence into others for as long as the fundamental awareness that one can be wrong is maintained?

Confidence is vital in general but I have seen people take one positive boost to their confidence and then try to universally apply it to everything. I guess my question is more about moderation, which to me would read as spaced-repetition + variety.

I get that confidence tricksters are a thing but what if there was someone that said stuff like "believe in yourselves first, and me last if you still need more than just yourself."