At first I felt a bit silly as I walked along with a smile on my face, but I quickly realized that no one minds if you’re looking happy. I also try to smile whenever I interact with someone—buying a cup of coffee, checking in at the gym, going through security before going up to an office (is it only in New York City that you have to show your driver’s license in order to go into an office building?).

Facial expressions don’t merely reflect emotions, they also affect emotions. In “facial feedback,” studies show, the mere act of smiling makes people happier—even when they smile mechanically, as I’m doing, or when they’re asked not to “smile” but rather to contract specific facial muscles.

Random smiling is an example of my resolution to “Act as I want to feel”: while people suppose that feelings inspire actions, in fact, actions also inspire feelings. So by acting happier, I should feel happier. And you know, I think I do. “Sometimes your joy is the source of your smile,” Thich Nhat Hanh wrote, “but sometimes your smile can be the source of your joy.”

Also, because of emotional contagion, people often mimic the faces of people they see. I’ve definitely noticed that people are much more likely to smile at me when I’m smiling.

The biggest challenge is to remember to do it. I’m reminded of my various efforts to improve my posture. I’m good for a little while, then get distracted and don’t think about it for the rest of the day. So I’ve been trying to use the sight of a traffic light as a prompt.

From 2006 through 2014, as she wrote The Happiness Project and Happier at Home, Gretchen chronicled her thoughts, observations, and discoveries on The Happiness Project Blog.