Happiness for others leads to happiness for oneself

Once a group of 50 people was attending a seminar.
Suddenly the speaker stopped and started giving each person a balloon. Each one was asked to write his/her name on it using a marker pen. Then all the balloons were collected and put in another room.
Now these delegates were let in that room and asked to find the balloon which had their name written, within 5 minutes.
Everyone was frantically searching for their name, pushing, colliding with each other, and there was utter chaos.
At the end of 5 minutes, no one could find their own balloon.
Now each one was asked to randomly collect a balloon and give it to the person whose name was written on it. Within minutes everyone had their own balloon.
The speaker began: This is exactly happening in our lives. Everyone is frantically looking for happiness all around, not knowing where it is. Our happiness lies in the happiness of other people. Give them their happiness, you will get your own happiness.
And this is the purpose of human life.