有人说，幸福是一种感觉，不知足永不会幸福，因此要学会“知足常乐”。

“知足常乐”，汉语成语，意思是知道满足，就总是快乐（A man who is contented will be happy），形容对已经取得的成就感到满足并取得快乐。与英文谚语“a contented mind is a perpetual feast”意思相近，表示“If you are mentally at peace, you will always feel that you have enough of everything, and will not have to strive to get more”。

例句：

A: 莉莲挣的钱不多，但她似乎一直很快乐。我想知道她是怎么做到的？

A: Lillian doesn't make very much money, but she seems to be happy all the time. I wonder how she manages that?

B: 知足常乐。

B: A contented mind is a perpetual feast.