I Am the Greatest!
Overconfidence might not be such a bad trait, at least from an evolutionary standpoint. In their article, "Evolution: Selection for Positive Illusions," Profs. Matthijs van Veelen and Martin Nowak observe that most of us overestimate our abilities and underestimate our exposure to risk.
That sounds like a recipe for disaster, but thinking you're the greatest (even if you're really just "pretty good") may actually offer an evolutionary advantage.
Martin Nowak is a Professor of Mathematics and Biology, as well as the Director of the Program for Evolutionary Dynamics at Harvard. You can find a complete list of Prof. Nowak's articles in DASH here.