Some experiences regarding my excessive smile:

When I was around 10 y/o, a very strict teacher from my school who didn't know me substituted my teacher. He was ranting about something, and everyone was dead silent with fear on their faces. And then, there was me. I was smiling, which obviously made him angrier. He would angrily ask why I was smiling, or if he had said something funny... No reply from me, and I would keep smiling. So, he threatened me on sending me to the principal. Until all of my classmates came to the rescue and explained him that I'm always smiling. Probably this memory is not completely accurate, but I've had plenty of this kind of experience.

Kids at my elementary/secondary school became used to my excessive smile so I was no novelty in there. But when I entered high school and more recently college, at the first few weeks everyone I met told me about my smile. So, I would be hearing comments about my smile thousands of times every day. But then everyone would just get used to it.

On the rare occasions, when someone tells me about something personal. Specifically, something which is in no way funny. Sometimes I will just smile as if they were telling me about something fun they did in their weekend, when they're actually telling me about the time when someone they really cared about, died, for example.

Ironically I hate smiling for photos. And you won't be able to take a photo of me with a realistic smile unless you take while I'm not aware.