This sentence comes from the Analects of Confucius, "Zi Yue Chuan, the deceased is like a husband, not giving up day and night."

Confucius stood by the river and said: Time goes by, just like this river, day and night.

This sentence is now used to sigh that time is like running water, which is gone forever. Lost time and lost world cannot be traced.

Therefore, people can neither indulge in the irreparable past nor waste the present extravagantly, but should grasp the present and cherish the time.

I hope I can help you ~