A few people have asked me for "the rest of the story" from the tag quote. So I will post the entire poem for you. Here goes. It was from page 123 of Chicken Soup for the Teenage Soul.
She smiled at a sorrowful stranger.
The smile seemed to make him feel better.
He remembered past kindnesses of a friend
and wrote him a thank-you letter.
The friend was so pleased with the thank-you
that he left a large tip after lunch.
The waitress, surprised by the size of the tip,
bet the whole thing on a hunch.
The next day she picked up her winnings,
and gave part to a man on the street.
The man on the street was grateful;
for two days he'd had nothing to eat.
After he finished his dinner,
he left for his small dingy room.
(He didn't know at the moment
that he might be facing his doom.)
On the way he picked up a shivering puppy
and took him home to get warm.
The puppy was very grateful
to be in out of the storm.
That night the house caught on fire.
The puppy barked the alarm.
He barked 'til he woke the whole household
and saved everybody from harm.
One of the boys that he rescued
grew up to be President.
All this because of a simple smile
that hadn't cost him a cent.
Barbara Hauck, age 13