Warren Buffett: 1987 Berkshire Hathaway Shareholder Letter

“Ben Graham, my friend and teacher, long ago described the mental attitude toward market fluctuations that I believe to be MOST conducive to INVESTMENT SUCCESS

He said that you should imagine market quotations as coming from a remarkably accommodating fellow named 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 interest 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

At times he feels EUPHORIC and can see only the favorable factors affecting the business. When in that mood, he names a very high buy-sell 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

Mr. Market has another endearing characteristic:

He doesn't mind being ignored. If his quotation is uninteresting to you today, he will be back with a new one tomorrow

Transactions are strictly at YOUR OPTION

Under these conditions, the more manic-depressive his behavior, the better for you”