For A Few ReasonsWhen I was a kid, my mother used to say that if I don't smile more I will have a bulldog's face before I hit my thirties. Thank you, mommy.
I look too serious mostly because I want to as few people as possible to see my smile. It's not pretty, and that is not only my opinion. It's hardly a smile at all, more likely a twisted grin. Usually, when I'm just moderately amused and not laughing out loud, only other corner of my mouth rises. It looks like... well, maybe you can picture it in your mind. When in public, I often try to look away from person or cover my mouth when I'm smiling.
The other reason is that I'm not too comfortable in large crowds of people, but neither in small gatherings. They look you into the eyes! Is that considered as good manners? In any case, it makes me nervous. I hate making eye contact for longer than three seconds. In order to avoid these awkward situations, I pretend I'm not even present or at least don't want to talk to anyone. This includes 'I won't smile even if your life depended on it' and 'I stare at the wall rather than look at you, that's how interesting you are' kinds of behavior.
So, I often look like I would be in funeral in social situations. This may be part of the reason I don't have too many friends. I'm not all that serious at heart, but I act like it nonetheless.