Teachers share many experiences, but one of the most eye-roll-inducing is the "I don't know why I failed when I think I'm brilliant" student. This semester, I had several of them, and, as usual, they were painful to deal with...and a few of them never did realize their true level of work. Similarly, all teachers can pull out tons of stories about students who firmly (fervently even) hold on to their misguided beliefs even in light of contradictory evidence. This past semester, I had a few which ignored anything that didn't directly support their own beliefs, and they did so with the tenacity of a wounded pigeon.
This is the hardest thing with which teachers must deal (other than online course management systems and administration, that is). I always tell my students that I will give them no answers, and that they will in fact leave my class with less certainty than when they entered. I tell them this, even though I suspect they don't believe me. But questioning everything, up to and including themselves, is in fact the desired state. I've always believed this.
Still, it's nice to have corroboration. This is why I was thrilled when I read We Are All Confident Idiots. It gives an overview of the science behind both the original overconfidence and the desired lack of certainty. I'm already violating my own Thou Shall Not Work Over the Break rule by trying to figure out where to fit it in to my Fall classes. And I strongly recommend all my teacher friends do the same.
I'm 100% absolutely certain they won't regret it.