I've been haunted all my life by having a face that looks depressed. I used to get classmates stopping me in the hall and asking if I was okay; co-workers going out of their way to make sure I was all right; and the guy who occasionally waited at the bus stop with me asking my dad if I was depressed (he usually waited for the bus with my dad).
I used to think all these people were crazy-nuts, until one day I was standing in front of a mirror and my thoughts wandered off into the land of dragons, as they are often wont to do. My face went from 'blank' to 'I'm about to cry' as my brow furrowed slightly in concentration on my thoughts. I guess that's what I get for trying not to display the emotions running through my head along with all my thoughts.
There was no way to explain this to others--especially since when I'm lost in thought I'm very well lost and it takes a map and a few minutes to relocate myself.
Eventually I got fed up with the constant 'are you okay?'-ing and started trying to smile all the time--nothing big, just a little smirk. It's been a mixed success. I feel happier all the time, and always believe that I'm smiling--but no one else can tell that it's not a straight face. This works well for telling jokes--except when people aren't expecting jokes, and I end upcoming across as a jerk, an idiot or someone very unhappy with current circumstances.