I work with two men who have been in the same business for 40 years. Both are within a few months of retirement.
One is confident and self-assured. He is a former president of his local professional society. He has a fairly loud voice, and he’s quick to tell you about his accomplishments. When asked a technical question, he always has a quick answer, never looking anything up. He says he ran his own business for before he joined our firm three years ago. He hasn’t told me why he stopped, but it has become clear. The quick answers are usually wrong. His work is embarrassing at its best. He claims to be an authority, but he is granted none.
The other is quiet and modest. More likely than not, he’ll be self deprecating as he shows you some of his brilliant work. When asked a question, he almost never has a quick answer. Instead it usually takes him some time to dig out his notes and work through a solution. Often, he’ll work late into the night to find the answer because he’s curious, too. He speaks softly, and I’ve never seen him upset. More than once, I have watched him silence a loud meeting without raising his voice. When he speaks, people invariably listen. That’s real authority.