I used to make my coworkers very nervous. They said I was (a) too happy and (b) too nice. It's an interesting turn of events when we reach a stage that smiling is suspicious and surliness is the norm.
On my little jaunt this past weekend, I encountered a LOT of people. They ran the gamut from extreme surliness to extreme pleasantness. What I noticed was the way that attitudes were contagious.
A nasty cranky woman waiting in the line for the restrooms as the fireworks infected everyone around her with her impatience and anxiety.
A friendly fast food worker sent everyone he dealt with on their way with a smile--a smile that lasted a long while.
My five year old granddaughter made our middle-aged waitress' day when she gave her a sunny smile and said, "You're pretty." There was nothing we could have asked for that would be too much for our waitress to provide.
Smile... it costs nothing.