June 15 is National Smile Power Day, and what better way to start the day than with a smile? Most people think that we smile because we feel happy, but it can go the other way as well: we feel happy because we smile.

In fact, the simple act of smiling, whether forced or genuine, spurs a chemical reaction in the brain, which releases dopamine and serotonin. Many people know those two neurotransmitters by different names; serotonin is often called the happiness hormone and dopamine the feel-good hormone. Therefore, a person's smile is a powerful tool for improving mood, de-stressing, and promoting positive feelings.

Scientists have long known that emotions are accompanied by numerous changes in the body. For example, fear can make our hearts race and humor can cause flexion of the zygomatic major muscle (i.e. a bend in the facial muscles that produces a smiling expression). However, science has come to understand more recently that the brain actually pays attention to what the body is doing. This was first called the "facial feedback hypothesis," but it applies to more than just muscles of the face. When our muscles say we're happy, we're more likely to see the world around us in a positive way.

The folk wisdom here is to fake it until you make it; our health may depend on it. After all, smiling can lift one's mood, lower stress, boost the immune system, and maybe even help a person live longer.

Furthermore, smiles are infectious. Even though faked smiles may not make the pretenders feel any happier, the people around them are more likely to smile, and in a reciprocal reaction, that can improve their mood as well.

The following tips may help:

• Force it: Since even a fake smile can increase feelings of happiness, the first step to being happier is smiling even when we don't feel like it.

• Find humor: When feeling down, we might watch a funny movie, read some jokes, sing a happy song, dance, whistle, or seek out another healthy humor boost.

• Engage with others: We are socialized to laugh and smile more in a group, so regularly spending time with friends can lead to pleasure. After all, staying connected and doing what we enjoy produces happiness.

• Think Positively: Life is really all about how we approach things. Even when going through hard times, looking for the good or the humor will positively impact our outlook, our health, and our overall quality of life.

Some readers are likely laughing right now (mission accomplished!), believing that achieving happiness is not that easy. That's true. We have to work to be happy. Too often people delude themselves with the conviction that life is responsible for their happiness; that people and conditions should be different.

The truth is that we are the authors of our own life stories. We need to constantly revise for the ending we desire. The wisdom that applies here is-if it's going to be, it's up to me. Happiness is an inside job resting on our shoulders. If the universe cooperates, that's a bonus, but the bottom line is-we have to create our own bliss, and that requires commitment and effort.

Dr. Russell Grieger agrees. In his Psychology Today blog post, "The Five Happiness Power Principles: The Root Source of All Happiness," he lays the foundation for how to systematically build happiness into one's life. Early on he quotes the wisdom of St. Francis of Loyola: "Pray as if it all depends on God, for it does; but work as if it all depends on us, for it does." He goes on to share several strategies that have transformational power.

So, on June 15, smile. Even though it's easy to slip into negative thoughts/reactions, we have the power to adjust that thinking. And it all begins with a smile.