When Zhuang Zi's wife died, his friend Hui Zi went to offer his condolences to the sage. He saw Zhuang Zi sitting on the ground, drumming on an upturned basin an singing. Hui Zi said to him, "Your wife lived with you, and gave birth to and brought up your children. The fact that you refuse to weep just because she became old and died is something that I can understand. But to drum on a basin and sing - is that not going beyond the bounds of decorum?"
Zhuang Zi answered, "That is not the case. When she died, of course I was grieved. But I realized that originally she did not exist. Then she had a shape and life, and then she died. That was just like the changing of the four seasons.
Now she is quietly lying in a big room. If I weep and wail, that shows that I do not understand the rules of nature. So I ceased weeping."
~Chuang Tsu, Zhuangzi