I’m trying to do a better job of laughing out loud. Studies show that a small child typically laughs more than 400 times each day, but an average adult laughs 17 times. I wonder if I hit even that number most days.

My Third Commandment is to “Act the way I want to feel.” If I want to feel happy and lighthearted, I need to act that way — say, by laughing out loud.

Laughter is more than just a pleasurable activity. Laughter can boost immunity and lower blood pressure and cortisol levels. It increases people’s tolerance for pain. It’s a source of social bonding, and it helps to reduce conflicts and cushion social stress within relationships—at work, in marriage, among strangers. When people laugh together, they tend to talk and touch more and to make eye contact more frequently. Usually, when we find something funny, it’s in spontaneous response to something that’s happened when we’re with other people.

I’ve been trying to find reasons to find things funny, to laugh out loud, and to appreciate other people’s humor. No more polite smiling; no more reluctance to be joshed and teased. One of life’s most exquisite pleasures is making people laugh, and by laughing, it’s obvious that I make other people feel great, which in turn makes me feel great. It’s almost heartbreaking, in fact, to see my daughters gaze into my face to watch my reaction.

The other morning, after my 3-year-old told me the same knock-knock joke for the tenth time, she got a little teary. “What's wrong, lovey?” I asked. “You didn’t laugh!” she wailed.

“Tell me again,” I said. She did, and the next time, and hearing the joke for the eleventh time, I laughed.