It's a new government directive requiring us to be 58% more cheerful within 18 months.
"Perhaps a dirge would lift your spirits?"
Say it with Flowers: Get well.
"I've come to the conclusion that there isn't anything you can say that will cheer me up or make it better!"
A vandal puts up 'Have a Nice Day' signs.
"Cheer up, grod, these are the good old days."