During morning rush hour, thousands of commuters flow out of Grand Central Station in a crazed swarm of humanity, scurrying and stampeding every which way, pouring onto the city streets, hurriedly and insanely, many not watching where they’re going because they’re text-messaging or talking on cell phones.

As they file out into Manhattan, there’s an exit on Lexington Avenue opposite 43rd Street, where a woman hawks newspapers and stuffs a copy into the hand of anyone who’ll take it. She smiles and shouts, “Good morning, Sir! How are you today! Read about …” Depending upon the big story, her pitch could be “There’s a cold snap coming!” “There’s a hurricane on the way!” “North Korea is at it again!”

She reminds me of the newspaper boys during the New York City circulation wars, who would notoriously chant “Extra! Extra! Read all about it!” back when people loved reading a newspaper more than playing Words with Friends or Candy Crush on their cell phones.

She’s so engaging that I pause in my morning dash to the office. She smiles broadly and makes eye contact and I almost feel obligated to take a paper. I WANT to take a paper. If she were in sales, I’d be tempted to buy overpriced whole life insurance or some worthless penny stock from her.

From the time I get on the train until the time I get off the train, I’m usually grim-faced and dour. But then, she looks at me and I look at her and I have to smile and respond, “Good morning to you, too!”

The great thing is I remember that moment throughout the day. Have you ever met anyone who could ignite your enthusiasm and make you feel good about life … just with a smile? It’s wonderful, it’s exhilarating, it’s a necessary part of our survival, especially in 21st century America.

Smiling is contagious. Joy is contagious. And so are anger and crankiness. But here’s the difference. Most of us would rather be joyful even if we won’t admit it, and a smile, particularly from a stranger, is a perfect intoxicant.

One Swedish study showed that when researchers showed a picture of a smiling person to a group and asked them to frown, they smiled instead. They had to force themselves to frown.

Mother Teresa was known for her joy and her smile despite the deprivation she confronted every day in Calcutta, and she once said, “Every time you smile at someone, it is an action of love, a gift to that person, a beautiful thing.”

That’s how we bring happiness to people — through giving more than getting, through actions more than words, through our example more than preaching. And why is that important? Because so many people are lonely and depressed, wandering in darkness and despair, and they don’t even realize it.

I confess that I have trouble smiling. I’m often startled when people say to me, “Why are you scowling?” “What’s your problem?” “You look angry.”

Urrrrgh, ogggg … I try to smile but it’s a struggle. Some of us have to relearn how to smile. As kids, it came naturally to us. The average person smiles 20 times a day. Happy people smile 40 to 50 times a day, but children smile an average of 400 times a day … so they’re clearly doing more to promote joy and friendship than the rest of us.

I certainly don’t want to be like a man I knew who came to work every day with a puss on his face. His negativity was contagious, and sad to say, we all rejoiced in it because there’s a morose gratification we get from group misery. Needless to say, the only time some people smile is when they’re gloating over another person’s misery.

Research also shows that good health and peace of mind are fringe benefits for people who smile. Smiling makes you attractive to others, according to a study by the University of Aberdeen in Scotland. You may not become a supermodel, but people will take notice. Smiling also activates endorphins and serotonin, which relax you, lower your blood pressure and elevate your mood.

And as Mother Teresa said, “We shall never know all the good that a simple smile can do.”

You may contact Joe Pisani at joefpisani@yahoo.com.