There is a well-known song in the LDS church that the children often sing, in Primary. When I was a boy, that was one of my favorite songs.
"If you chance to meet a frown, do not let it stay. Quickly turn it upside down and smile that frown away. No one likes a frowny face, change it for a smile. Make the world a better place by smiling all the while."
There is simplicity in the message of that song, but I believe, wholeheartedly, that if the people's of the world fully understood the solid principle, that this children's song teaches, it would make for a better place to live.
A simple smile is a very small means in bringing someone else a great amount of joy.
I ask myself, "Do you smile, so that people know that you are happy?" I think I can improve in this area.
A person walked by me, today, and their smile encompassed their whole face. When they smiled, it made their eyes smile, too. It was fun to recognize that and to instantly feel of their joy. That's how I want to be.
The world ought to know that no matter what I'm doing, I am happy. They will know that how I feel about my life is directly reflected from the smile that I display.
Remember the words to the primary song. It stands as a perfect reminder for me.