Epistemic status: anecdotal evidence which I believe can be generalized.
An insight I had in the last few months is that self-confidence has a positive side-effect above and beyond the positive qualities usually associated with it. What I mean is: we've all heard of “just believe in yourself” is the panacea to nearly everything: this is about something different.
Self-confidence is an invaluable way of doing things quickly and efficiently, saving mental resources.
To illustrate my point, I’ll use a real life example: when encountering a problem during work (or study, or starting a relationship, or something else) a person with low confidence will usually agonize over what to do, seek outside advice, validation or orders, in an effort to take the “safe” path.
This has consequences; speaking personally, I had a horrible experience in a past job partly because of this; every question was met with scorn because I didn’t already know what I was supposed to do, or because “it’s obvious! Why are you even wasting my time?!?”.
This made me more insecure, thus leading to me stalling more when encountering something outside of my immediate area of expertise, agonizing over whether to ask questions or not, and so on and so forth.
As an aside, even though asking question is usually said to be a virtuous thing by everyone, this is not so in reality: there are stupid questions, and more to the point, there are questions that if voiced, will hurt your social standing and make you look stupid. Questions that, even if answered, aren't really worth the cost. (No one will volunteer to tell you what those question are. You have to figure it out yourself).
The crucial point of this is that by not asking questions/for orders and using their own judgment, a person is taking a risk (sometimes a very big risk, sometimes just what feels like one).
Except that sometimes taking a big risk is the correct thing to do.
Yes, even if the risk does not pay out and your boss/teacher/significant other berates you for half an hour and makes you feel like the lowest of worms.
There are obvious costs to this: taking risks, is, well, risky. The crucial decision to make is: is the time and reputation preserved by doing this worth the probability of failure?
A way of thinking about this is as an approximation: you treat the fearful/unknown situation as if it were something you already know how to do. In math, statistics, physics (most science actually) this is a necessary step to take, because one cannot wait for a couple of years while a computer calculates the trajectory of every single air molecule, but one can use the equation PV=n R*T which is almost as good.
The social downside of this is called arrogance and cockiness, which are thing that have to be managed to keep good relations with your peers. Still, it is a very good way to conserve resources, both in time and mental energy.
Exercise for the readers:
The last time you took a risk and acted like you knew what was going to happen when you actually didn’t, what happened?