Admit when you don't know

Similar to admitting when you are wrong, it's important to realize when to admit what you don't know.  There is a power in it.  As Harvard Business School writes,
"Many managers are afraid to utter things like: "I don't know," "Would you help me?" or "I'm not sure I get it." But failing to admit when you make a mistake or lack knowledge makes you less effective. When you pretend to know everything, you miss opportunities to learn. And if you try to hide your ignorance or your errors, you'll lose peoples' trust. They know when you don't know something or make an error. Fess up when you're in those situations. Acknowledge your own limitations so others can do the same. And when you need it, ask for help and be open to learning."
I think it's fair to say, we are never too old to keep learning.