Scott Adams, the creator of Dilbert, said in his blog...
The reality is that there are only two conditions you can be in. You can either have an accurate view of your own abilities or an inaccurate view. Confidence is similar to will power in the sense that neither of them exists and yet society is quite certain they do.
I'm not sure I agree that our view of our abilities is either "accurate" or "inaccurate". How do you measure the accuracy of our perceptions? Isn't that something that is subjective by nature? As Scott admits later in his article, it is often useful to be "inaccurate" in how you perceive your own abilities. For one thing, there are too many variables in any given situation to accurately predict with 100% certainty so we are always going to be inaccurate about our abilities to some degree. If it were possible to predict with 100% certainty, then where would the fun be in that?
Growth vs. Talent Mindset
It seems that Scott may have fallen into the "Talent mindset"which says that either you are good at something or you are not. If you fail at something, then don't bother trying again because you don't have the inate talent for it. The Growth mindset is very different. It says that any one outcome is simply an indication of how far you are along your progression to eventual success.
This is where confidence can play a key role. If you are using the Growth mindset and have failed in the past, your confidence can still be high since every outcome is simply feedback on your way to success.
Confidence is important because it gets you to TAKE ACTION. As a famous philosopher once said, "80% of success is just showing up" and confidence gets you to "show up". (I think it was said by Woody Allen.)