The balloon experiment and a lesson for everyone!
A teacher gave each student a balloon to write their name on. He then shuffled them all into the hall and told them to find their balloon. They had 5 minutes.
Despite the great effort, no one managed to find their balloon.
Then the teacher told them to grab a balloon and hand it to the person it belonged to.
After 5 minutes each student had his balloon in hand.
Then the teacher said:
These balloons are like happiness. We will never find it if everyone is only looking to find their own. If we also care about the happiness of others, we will find our own too.