The informant learned the proverb from her mother.
“It means that when you meet people you never know what their real life is like at home when nobody’s watching. It stuck with me because as I’ve grown older, I realize how true it is for so many people. I mean you read the papers and see these horrible things happening to children. Sexual and physical abuse and verbal abuse. People hiding these things. And I think she had that in her family. She had an abusive father. It was her own very quiet way of telling me, [the proverb]. She was saying ‘be understanding about other people when they may not be acting perfectly because you don’t know about their lives.’ Have empathy. I think that’s what she was trying to say. Even if their not perfectly nice, maybe they are coming from a place that they need more understand than the average person.”
The informant said that she would tell this to her children when they had issues with others in school. Sometimes she would see signs of something awry in their lives that would make the child act out. The informant wanted her children to be compassionate like her mother had taught her to be.
Annotation: Denise Richards utilizes a variation of the proverb commenting on the difficulties in her life with Charlie Sheen in an interview with Fox 411:
McGevna, Alison. “EXCLUSIVE: Denise Richards: ‘No One Knows What Goes On Behind Closed Doors'” Fox News. FOX News Network, 10 Feb. 2011. Web. 21 Mar. 2013. <http://www.foxnews.com/entertainment/2011/02/10/denise-richards-people-quick-judge-situation/>.