I literally learn something new every day.
Most of the time, it's from a student's question while I'm working at the reference desk. A lot of it comes from ITE students (the computer class where they have to learn every minute detail about Word, Excel, Powerpoint, Publisher, and Access, regardless of how useful it might be in their future). I find a new way to do something I've been doing for years, or I discover some feature I didn't know existed.
Today, I used the Help menu on a piece of graphic software I've been using since elementary school, because something I thought I knew how to do just wasn't working right. I discovered an entirely new toolbar that I never knew existed, and is incredibly helpful.
Yesterday, I read an article from the Chronicle of Higher Education about interviewing for jobs in academia. One of the bits of advice was that you shouldn't be afraid to admit that you don't know something. Of course, if you find yourself not knowing a lot of things, you should reconsider your candidacy for that position, but it's not shameful to not know something; it's shameful to pretend you know something and get caught in the lie later on. Who knows? You might learn something.
So what I'm saying is, if you can admit that you don't know everything about something (in my case, the software I've used for 80% of my life) you could learn something new that makes you even more knowledgeable in that area.