Given the task definition and input, reply with output. In this task, you're given an article and an answer. Your task is to generate the fill-in-the-blank question for this answer based on the given article. The blanks are always at the end of the question, and can be filled with more than one word or phrase.

Article: Happiness is like a stone dropped into a pool to set in motion an ever-widening circle of ripples . As Stevenson has said, being happy is a duty. There is no exact definition of the world happiness. Happy people are happy for all sorts of reasons. They key is not wealth or physical well--being, since we find beggars, patients and so-called failures who are extremely happy. Being happy is a sort of unexpected dividend . But staying happy is an achievement, a victory of soul and character. It is not selfish to struggle for it. It is, indeed, a duty to ourselves and others. Being unhappy is like an infectious disease; it causes people to stay away from the fufferer. He soon finds himself alone, miserable and upset. There is, however, a cure so simple as to seem, at first glance, ridiculous: If you don't feel happy, pretend to be! It works. Before long you will find that instead of repelling people, you attract them. You discover how deeply rewarding it is to be the center of wider and wider circles of good will. Then the _ becomes a reality. You possess the secret of peace of mind, and can forget yourself in being of service to others. Being happy, once it is realized as a duty and established as habit, opens doors into unimaginable gardens crowded with grateful friends.
Answer: Being Happy Is A Duty
The best title of the passage is_.