Just a short note from my side. There is nothing wrong with confidence but often the line between confidence and overconfidence is very thin. Overconfidence is the root of many massive fails, especially in finance, as it often results in excessive risk-taking.
From my experience, you should apply extra caution whenever someone guarantees a maximum drawdown or a bulletproof system. Everyone should be aware that this just isn't possible and to me, those claims are just an indicator for overconfidence.
Personally, I prefer the humble approach as presented by integracore2. Very often though, those that are outgoing, loud and overconfident are rewarded with decision making positions as they are perceived as competent (especially in finance) ... I wish we had more woman in this business. However, that's another story