We are happier when we smile. I don't have to tell you that; entire books have been written about the astonishing power of smiling to create sparkles in life. Scientists have run many long term experiments, tallied zillions of data points, made tons of first-person observations, taken loads of surveys, compared notes on discoveries. They have confirmed how voluntary smiling changes brain activity making you look, act, and feel smarter.
These ideas aren't new to you. You have the first-hand experience with smiling. I'm sure you've smiled once or twice in the past and seen how the situation was transformed by your smile.
You're making your world by smiling with it. Smiles get reflected back from what is smiled at in a feed-back loop like a snowball gains size as it tumbles down the hill. You feel happy, and that makes you smile. But it works both ways: when you smile, your brain can detect this.
"I'm smiling. That must mean I'm happy."
So happiness makes you smile, but smiling can also produce happiness.[^1]
Don't hold your smile ransom thinking you'll get around to smiling in the future when all your to-dos are done, when your health is perfect, when all your desires have been met, and all the news is good. At random times during your day, notice if you have a sullen expression. Notice how you hold your face when you read, when out on a walk when preparing dinner for your family, notice if you are smiling. Then just smile, observe the results, and tally another data point in the grand experiment of your life.
References
[^1]: Neuroscience Discovers 5 Things That Will Make You Happy