Don't feel bad, it's not your fault. The only thing betraying your true age is the fact that you even think about privacy settings. Most Facebook users have no idea how to limit (or judge) message visibility, nor do they desire to. Facebook also sabotages such attempts on purpose.

For instance, I used to think I got my publication settings down pretty good (by dividing FB friends into groups), but it turns out Facebook ignores and resets your preferences every once in a while for good measure. So even if you belong to the small minority of users who go through the trouble of trying to compartmentalize their message publication, Facebook will override you and enable interesting things like your coworkers commenting on party pictures they shouldn't even be able to see.