The document tells a story about a taxi driver in New York who taught the author an important lesson called "The Law of the Garbage Truck." When another driver cut them off and yelled at them, the taxi driver just smiled and waved at them. He explained to the author that many people are like garbage trucks, full of frustration and anger, and if you let them they will dump it on you. The lesson is that when someone tries to dump their garbage on you, don't take it personally - just smile, wave, and move on. Successful people don't let garbage trucks ruin their day.