When people take pictures, I'm very mindful to smile. I do smile, laugh, etc.. without a camera. However, my "neutral" face apparent looks upset. I can sit somewhere completely indifferent and people will often ask "Are you okay?"
I'm usually okay. It's just me....
I also try to be mindful about how I express myself during gift giving. If I love a gift because of the sentimental meaning, I will smile. If it's just a practical gift that I like (and possibly even asked for), I can remain neutral and neutral looks upset. I've offended several with this.