What is the historical lesson of "hiding the knife in the smile, falling all over the country"

1, ruler, don't covet women, or you will regret it and bring disaster to the country and people.

2. Source of the story: "The Warlords in the Fire Play" tells the story of Zhou Youwang, who is fatuous and cruel, ordering people to light a bonfire and tease the princes in order to win a smile from his concubine. Zance really smiled. Wang You was so happy that he lit the bonfire many times. Later, the princes did not believe it and gradually stopped coming. Later, the dog army attacked Haojiang and killed Zhou Youwang. Later, Zhou Youwang's son Zhou Pingwang ascended the throne and started the Eastern Zhou Dynasty.

3. There is a similar story that follows "The world of mortals rides a concubine and laughs, but who knows it is litchi". Tang loved Yang Guifei, and made the soldiers sweat profusely, which made them miserable. ...