Have you ever been walking down the street and been so engrossed in a rather upsetting thought in your mind that you've had a perpetually distraught look on your face? Have you ever seen anyone else like this? How did that make you feel? Think about the moments when you've seen someone smiling. Even if it's just to them. How did they make you feel?

Feelings are of course very subjective, but generally people model behavior. You see someone smiling and laughing, and you don't have a reason not to join in, so you smile to yourself too. People's positivity rubs off on you. In the same way, when someone is in a bad mood, it doesn't take much for you to have your mood spoiled either.

How many times have you walked down the street and passed by someone you know, and you've exchanged a smile and a "Hey!"? How did that make you feel? How many times has someone passed you by and not acknowledged you, and how did that make you feel? These questions may seem incredibly arbitrary, but they're designed to illustrate how important it is to pay attention to the people around you and the way you're presenting yourself.

Even just passing by smiling or frowning strangers can make you feel differently, however subconscious or subtle the feeling is. I've tried to adopt the principle in life to always be a smiling persona, no matter where I'm passing by, I should always find myself smiling. Or at the very least, not frowning.

A simple smile goes a long, long way, as we've all heard. In fact, some studies have shown that a simple smile, even shared among strangers, makes people feel as though they already know each other. The science behind that theory has to do with our ancient ancestors, where human survival depended on groups, so humans would smile as a way to show friendliness to one another. The tiny smile that you see on passer-by's faces?

That actually has some real scientific reasoning, called subliminal priming, that backs up why you feel more positive or happier. Mirroring has been researched too; people mimic what they see. Even if it's just for a fleeting second, you mimic the smiles that you see in a crowd of people.

Think about how many times you've been served coffee by someone with a smile. A real smile, not a fake, half-smile that just made you feel uncomfortable. Those experiences usually leave you with the best customer satisfaction, right? Employers actually work that kind of training into their customer service models, for this exact reason. Seeing a smile makes you smile, and smiles mean you're happy.

So, all in all, spreading positivity can be as simple as putting a smile on your face when walking down the street.