Smile!

"Smile" is a song, originally used as an instrumental theme in the soundtrack for the 1936 Charlie Chaplin movie Modern Times. Chaplin composed the music. While some believe the words were written by John Turner and Geoffrey Parsons, the sheet music was sold with the lyrics accredited to Chaplin. In the lyrics, the singer is telling the listener to cheer up and that there is always a bright tomorrow, just as long as they smile. "Smile" has become a popular standard since its original use in Chaplin's film."

 Fonte Wikipedia