I've been noticing a lot lately that people aren't giving a courtesy wave when appropriate. For instance, when another driver lets you in a lane in heavy traffic, you should courtesy wave. As a pedestrian, if a driver stops to let you cross the street, you should courtesy. These are just a couple examples.
Now, I realize that lifting your hand and giving a slight wave could be a bit strenuous. I mean, you could have just come from the gym or maybe you just changed 100 light bulbs and your arms are really tired. But suck it up, and give a little wave. Or maybe someone put super glue on your steering wheel. Then give a nod or something. It's just polite and courteous and helps our society maintain a certain level of kindness.
We have to acknowledge the smallest acts of kindness before they are completely absent from society. So please, continue to give a courtesy wave, even if you're not sure it's necessary. The world will thank you for it.