I am a relatively young librarian, as I went straight from undergrad into grad school. I am not much older than my students; in fact, many of them are the same age as my younger sister (which makes it weird, because my sister is my best friend). Anyway, I was at a function the other day (ok, ok, church lunch), sitting at an adult table, and everyone who sat down wanted to know if I was a student, and how my studies were going. The same thing happened with my student workers: oh, are you a new student here? No, I'm not.
Whenever I talk to my co-workers about it, I receive the typical "adult" response: well, enjoy it while you can, that won't last long, let's talk when you're thirty. These responses irk me probably as much as when I am mistaken for a student. The reason is probably not what you think. I am not concerned about my peers taking my abilities seriously; there is one thing that I am really good at in life, and that is academia. I am not concerned about students taking me seriously, because they're students. What really worries me is that I won't take myself seriously.
I have been a student for the past umpteen years of my life. It is what I know. I am concerned that I will fall into old patterns. I don't really see myself as an adult at all - in fact, sometimes I worry I act like I'm still in high school. This job is important to me, and I don't want to mess it up because I cannot act like an adult. So every time someone asks if I'm a student, I wonder: am I student? Wait, no, I'm a librarian.