As you express joy, you draw it out of those you meet, creating joyful people and joyful events. The greater the joy you express, the more joy you experience.
When the historian, Charles A. Beard was asked about the lessons from history, he said there were four: 1. The bee fertilizes the flower it robs. 2. Whom the gods would destroy, they first make mad with power. 3. The mills of God grind slowly, but they grind exceeding small. 4. When it is dark enough, you can see the stars.
Down deep we really know our worth, but we don't have easy access to that knowledge. We need to hear praise coming from outside ourselves or we won't remember that we deserve it.