Play.
Remember when you were a child and you could just play. You could play and it made you smile and made you feel so happy. Remember the simple pleasure of just having play time, it was the best time of the day.
Go and find the bubbles, or the hopscotch, or the swings, or the game, or the musical instrument, or the crayons, find them and play. Let your inner child have the power again. Play with others, laugh and smile, enjoy this simplistic happiness again.
If you're not convinced, there is research now that shows that playing is just as effective as going to the gym in relation to weight loss. The added bonus is that it makes you smile during the process.
Playing was where the fun began. So don't neglect your inner child any longer, they might throw a horrible tantrum if they're not attended to soon!