It's nice to have a nice day. But it’s great to have a joyful day. Wish people a joyful day. Compare the standard “Have a nice day,” with “Have a joyful day!” What kind of a day would you prefer to have?

It would be incongruous to say, “Have a joyful day!” in a dull tone of voice with a sad look on your face. So allow yourself to experience joy when you wish others joy.

What will happen when you regularly wish people a joyful day? Experiment and see.