“The greatest bear is a sold out bull” (Wall Street adage)

Once an investor has sold a stock, it’s satisfying if the stock then goes down (providing evidence that the sale was at the correct time). If the stock goes up after a sale, the investor possibly didn’t sell for the right price.
 
“The greatest bear is a sold out bull” (or “The biggest bear is a sold out bull”) has been a Wall Street saying since at least the early 1900s.
 
   
9 August 1903, Philadelphia (PA) Inquirer, first section, pg. 15:
You must have first bear conditions before the bear traders can do effective word, and usually the most ferocious bear is a sold out bull. 
 
18 August 1903, Wall Street Daily News, pg. 2:
The reactionist, who is a sold out bull, has taken the place of the bear, and he is crying for a setback so that he can obtain a line of cheap stocks.
     
Google Books
Psychology of the Stock Market
By George Charles Selden
New York, NY: Ticker Publishing Company
1912
Pg. 83:
Indeed, it is a sort of proverb in Wall Street that there is no bear so bearish as a sold-out bull who wants a chance to repurchase.
 
19 September 1916, Philadelphia (PA) Inquirer, pg. 13:
There is no bear temporarily like a sold out bull as the saying of the street goes.
 
6 October 1916, New York (NY) Times, “Topics in Wall Street,” pg. 14:
It is an ancient saying that no bear is so bearish as a sold-out bull, and this would seem to have application now.
     
Google Books
Auditing Theory and Practice
By Robert Hiester Montgomery
New York, NY: The Ronald Press Company
1922
Pg. 345:
The greatest “bear” is the sold out “bull.” No one cares to acknowledge that he sold too soon or for less than his property was worth.
   
Google News Archive
3 July 1925, St. Petersburg (FL) Independent, “Stock Market New High,” pg. 8, cols. 1-2:
It is an old Wall street quotation that “the greatest bear is a sold out bull.”
   
Google Books
Why You Win Or Lose:
The Psychology of Speculation

By Fred C. Kelly
Published by Courier Dover Publications
2003
Pg. 28:
“The biggest bear is always a sold-out bull.”
   
Google Books
Ten Years of Wall Street
By Barnie F. Winkelman
Published by Cosimo, Inc.
2005
Pg. 263:
The old maxim that “the most rampant bear was a sold-out bull” found its corollary, that the same bear duly chastized, and in the bullish ranks once more became a mainstay of the continued advance.
and in the bullish ranks once more became a mainstay of the continued ...