When I'm letting myself be idle after a full day of anything, I notice myself thinking about the people who smiled at me that day.

Their smiles have the power to affect my thoughts hours later.

This past Sunday, I was driving in a residential neighborhood of Los Angeles. As I was creeping forward to make a right at a stop sign, a jogger was there to my left. I saw her, turned to glace at traffic, and as I turned, I caught her giving me a casual "hello" in the form of a smile. I'd almost missed it and had to do a double-take to acknowledge and return it. She didn't have to smile, but she did anyway.

The week prior, I had a video chat with someone who was already glowing by the time I logged on. I felt so happy immediately, and it really set the tone for the rest of our meeting.

I still think about a man in his car who I encountered over six months ago while driving. He was smiling out his car window, directing his smile directly towards me. It wasn't an aggressive or over-eager smile; instead, it felt welcoming and excited.

In all these instances, the smiles were surprises. I didn't expect any of them, and so that makes them all feel like bonuses. Like icing on the cake. They're little strokes of luck that I cannot create on my own.

And they aren't free! Every time you smile at a stranger, you make yourself vulnerable. Have you ever smiled at the wrong stranger? It's not fun. I've taken a gamble on some of the wrong people in my neighborhood, and they don't see smiling as a kind gesture at all. The worst ones curse and scream at you in reaction to a smile.

Or there are people who try to grab hold of your attention like a dangling lifeline they won't let go of. Maybe they're needy or exploitive. Either way, you find yourself regretting giving them the time of day.

So a smile is more than just a gesture; it's somebody betting on you. They're wagering that you're a person who is worth some amount of their attention. They're reaching out, hoping that you'll meet them halfway and make it worth their while.

And there's magic in that leap of faith.

The jogger on Sunday took a leap with me. I definitely wasn't prepared. I was ready to pull into the intersection, giving her just enough notice to be sure that I wouldn't drive into her and nothing more. If she hadn't smiled, then nothing would have happened, and I wouldn't be writing about our encounter right now.

The funny thing is that I'd never be able to pick her out of a lineup if I had to. I can't remember what she looked like for the life of me. But I remember how she made me feel. I remember that she made me feel one inch more a part of the Sunday afternoon I was driving through. I remember that she pulled a genuine smile out of me just by going first.

I'd be hard pressed to list the times when somebody else felt good because of a smile I gave them. I can only think of one where I saw a girl in a batman T-shirt roller dancing like a boss at Santa Monica Beach, but I think that's because I was struck by her musicality and her general excitement about roller dancing. Other than that, it's just not something I can recall on-the-spot.

And so I forget sometimes how powerful a smile can be. And I fall out of touch with the impact of one until somebody else gives it as a gift back to me. And then I remember, because I get to experience the warmth of a "hello" I wasn't expecting. It's so powerful that I consciously notice the moment and the other person who helped create the moment. I remember how it feels, and so I remember why paying it forward is important.

If you take anything away from this, I hope it's just that there are people out there who are eager to make someone's day with a smile, and all it takes is being aware enough to allow that connection to happen.