You're in traffic when you notice someone in the next lane has their blinker on and wants to get over. You slow down and make sure there's ample room, and they drift in front of you.
Then... no wave.
Do you throw a courtesy "thank you wave" when someone lets you in? If so, you probably look for this show of appreciation when you're the one making space for another driver, but what happens when they don't wave?
At first, it rather feels like the kindness you put out into the world never even happened if they don't acknowledge it. I mean, why ever do anything nice for other people if it's going to go unrecognized?
C.S. Lewis said "integrity is doing the right thing even when no one is watching," or, in this case, when someone should've been watching but totally ignored your gesture. So, in order to have integrity, we have to let people walk all over us? Not at all. The truth is, when we do something nice for someone else, we should promptly move on and not consider the other person's reaction at all. In a study published in the journal Emotion, researchers discovered that doing nice things for others - irrespective of any payoff - actually increased the happiness of those doing the good deeds.
Call it "sowing and reaping" or "growing character" or whatever you like, but doing nice things for others makes us happier than focusing on doing nice things for ourselves. So, be selfish and let someone cut in front of you, buy the coffee of the person behind you in the coffee drive thru, or just leave someone an anonymous "thank you" note.
Then, don't wait for the reward to come from that person. Your reward is that you'll be happier.