We all overestimate how much we know. If the aphorism, “the more you know, the more you know that you don’t know” is true, then how else could it be? But knowing more is not the only path to learning about our ignorance. Mistakes are another. When we make mistakes, we get to adjust our parameters (understanding) about how much we know. Overconfident people, however, incur smaller losses when they make mistakes. They don’t learn as much from mistakes because they externalize the source of errors or don’t acknowledge the mistakes, believing it is you who is wrong, not them. So, the most ignorant (the most confident) very likely make the least progress in learning about their ignorance when they make mistakes. (Ignorance is just one source of why people overestimate how much they know. There are many other factors, including personality.) But if you know this, you can fix it.