How can you tell if someone really knows what they’re talking about?

 Ask them what they “don’t know” about the subject. If they are as enthusiastic as they were telling you what they do know, you’ve got someone who can see enough to know what they can’t see yet.

Surprising confidence hack

Confidence is the acceptance of vulnerability.

Confidence

Maybe it's not 'being confident' but what being confident brings that makes it important.