Before this text gets too long and I start rambling, I guess the conclusion I'm trying to steer towards to is: kindness - starting at a smile or an entire conversation - can improve each and everyone's lives. Not only do you improve the person's experience you've been kind to, but (and this sounds very karma-related) it comes back to you! Be kind to others and they will (most likely) be kind to you. Not that hard, is it?
"The highest form of wisdom is kindness." - The Talmud