Possible Clues:

• Stay on cloud nine
• Advice from Bobby McFerrin
• "Cheer up!"
• "Don't worry, __" – Bobby McFerrin's advice?
• 'You should smile more'
• "You should smile more"
• 'Don't Worry, —' (Bobby McFerrin hit)
• Pep talk directive
• End of a Grammy-winning McFerrin song title