在《詩經》中，以「喜」來表達個人內心愉悅的情感，《左傳》有「喜」、「懼」連用表達喜悅與懼怕並存的情感。「喜」並非「樂」，《詩經》中的「樂」有不滿現實生活，嚮往理想世界之意。《論語》承襲《左傳》對「喜」的理解，以「喜」、「懼」連用表達子女面對父母的生及其可能有的死時內心的複雜情感。在《論語》中，「喜」是可轉化的情感，「樂」則不同，屬於深層情感，本身不可轉化，只能被經驗和感受，而「憂」與「喜」相似，屬於可轉化的情感，故而，孔子有「樂以忘憂」的言說和情感經驗。孔子的「樂以忘憂」之「忘」，在哲學思想傳承上影響到後來的莊子。而孔顏之樂，實是以樂道之心，忘憂貧之情。

In Book of Poetry, Xi (delight) has already been used to express the feeling of delight in a person’s heart. In The Tso Chuen, the author used Xi (delight) and Ju (fear) to explain the internal feelings which contain pleasure and fear. Xi (delight) is not Le (Joy), the poets used to say that one is not satisfied with his usual life, and aspires to the ideal life in his heart. Being influenced by the understanding of Xi (delight) in The Tso Chuen, in the Analects Confucius used Xi (delight) to illustrate the phenomenon that when children facing the still living and doomed uncertain coming death of their parents, their heart experiencing a kind of complicate emotions which combine Xi (delight) and Ju (Fear). In the Analects, Xi (delight) is the kind of emotion, which can be transformed into other emotions, but Le (Joy) is different, it belongs to the inner feeling which only can be experienced and not be transformed into grief, fear, anger, hatred, etc. Besides that, You (Worry) is akin to Xi (delight), it is a transformable emotion. Therefore, Confucius has the teaching and experience of “who in the joy of its attainment and forget his sorrows”. “Forget” in the “who in the joy of its attainment and forget his sorrows” has directly effect on Zhuangzi. And the joy of Confucius and Yanhui is in fact forgetting the emotion of worries about poor by loving Dao with a joyful heart.