I've been experimenting with mindsets and observing outcomes of different mindsets in regards to confidence.

E.g.

I believe I can do this because I'm lucky...
--- The likeliness of the person doing what they believe they can do depends on how much faith they put in luck and how lucky they believe they are. The concept of luck for most people is pretty shaky, so those who put a lot of faith in luck will likely have somewhat shaky results in things they do.

I believe I can because I have the skill required to do so.
--- The likeliness of the person doing what they believe they can do depends on how much how they compare their level of skill to others they may be competing with. So it's pretty consistent, depending on their opposer.

I believe I can because I've done it before.
--- This is one of those blind faith scenarios, it's powerful, but not %100 stable. If this person ever doubts themselves for even a second, because they have no logical ground to "how" they were even able to do it in the first place, they may lose their grounds on which they stand (because they've done it before)

Those are just a few examples of the type of mindsets I've experienced through natural life path and intentional experiments, personally. I will share my further results here as well.