If you are happy, and work on your happiness, you are contributing indirectly to other people's happiness, just like the baby who laughed last time-- made you laugh.

你快乐并努力争取快乐，就是间直接对他人的快乐作出贡献，就像上次大笑的婴儿，把你们逗笑。

哈佛公开课 - 幸福课课程节选