The Tale of "Mr. Market" as told to Warren Buffett by Benjamin Graham.
From the book Storytelling for Financial Advisors
by Scott West and Mitch Anthony
You should imagine stock quotes as coming from a remarkably accommodating fellow name Mr. Market, who is your partner in a private business. Without fail, Mr. Market appears daily and names a price at which he will either buy your stock or sell you his.
Even though the business that the two of you own may have economic characteristics that are stable, Mr. Market's quotations will be anything but. For, sad to say, the poor fellow has incurable emotional problems.
But like Cinderella at the ball, you must heed one warning or everything will turn into pumpkins and mice: Mr. Market is there to serve you not guide you. It is his pocketbook, not his wisdom, that you will find useful. If he shows up someday in a particularly foolish mood, you are free to either ignore him or to take advantage of him, but it will be disastrous if you come under his influence.
At times he waxes euphoric and can only see the favorable factors affecting the business. When in that mood, he names a very high price because he fears that you will snap up his interest and rob him of imminent gains.
At other times he is depressed and can see nothing but trouble ahead for both the business and the world. On these occasions he will name a very low price, since he is terrified that you will unload your interest on him. Under these conditions, the more manic-depressive his behavior, the better for you.
One other fella we might mention here is Mr. Market's best friend, Mr. Media. Mr Media loves to take his cues from Mr. Market and shout them in the streets and over the airwaves.
One day it is, "The market is up 100 points - buy everything!" The very next day Mr. Media shouts, "The market is down 100 points - run for the hills!"