A teacher once brought balloons to school and told her pupils to blow them up and write their name on one. After the children tossed their balloons into the hall, the teacher moved through the hall mixing them all up. Then the kids were given five minutes to find their own balloon. They all looked hard, but nobody found their own balloon.
Then the teacher told them to take the balloon closest to them and give it to the person whose name was on it. In less than two minutes, everyone was holding their own balloon. The teacher told the children, "These balloons are like happiness. We won't find it when we're only searching for our own, but if we care about someone else's happiness, this will help us find our own."