American money manager Barton Biggs (1932-2012) said in February 1996:
   
“Bull markets are like sex—they feel best just before the end.”
 
American investor Warren Buffett used Biggs’ saying in a 2014 Berkshire Hathaway annual letter to shareholders:
 
“A bull market is like sex. It feels best just before it ends.”
 
The quote is frequently—and incorrectly—credited to Buffett.
   
       
Wikipedia: Barton Biggs   
Barton Michael Biggs (November 26, 1932 – July 14, 2012) was a money manager whose attention to emerging markets marked him as one of the world’s first and foremost global investment strategists, a position he held—after inventing it in 1985—at Morgan Stanley, where he worked as a partner for over 30 years. Following his retirement in 2003, he founded Traxis Partners, a multibillion-dollar hedge fund, based in Greenwich, Connecticut. He is best known for accurately predicting the dot-com bubble in the late 1990s.
     
10 February 1996, Vancouver (BC) Sun, “U.S. Market Ready to Fall, Brokers Told,” pg. C8:
SINGAPORE—The U.S. stock market is heavily overvalued and likely to fall sharply in the next year or so, Morgan Stanley Asset Management chair Barton Biggs said on Friday.
 
Biggs, who surprised many people two years ago when he declared he was “maximum bullish” on Hong Kong, said U.S. investors were being carried along by a misplaced belief that the market could not fall. “Bull markets are like sex—they feel best just before the end,” he said. But he added that the bubble would burst and future growth would be elsewhere, probably in Japan and the rest of Asia.
 
Google Groups: misc.invest.technical
The Amenrick Market Report
Larry Amernick
2/12/96
THE AMERNICK MARKET REPORT
Vol. 2 #7
02/11/96
(...)
Barton Biggs, the chairman of Morgan Stanley Asset Management, warned that the U.S. stock market was getting overvalued. Biggs commented, “Bull markets are like sex—they feel best just before the end.” Biggs predicted that a 30%-40% correction is coming. “We are on the verge of a really serious bear market. The U.S., instead of being the best of the world’s markets, is going to be the worst.” His time frame is sometime in the second half of this year or early next year
 
2 March 1997, Morning Call (Allentown, PA), “Filmmaker Lou Reda Chart’s Remarkable History of the Dow” by Frank Whelan, pg. F1:
But with about 55 other students, Fonzetti watched a preview last week of Easton filmmaker Lou Reda’s latest program, “Dow Jones, Wizards of Wall Street,” that will be seen on the Arts and Entertainment network’s Biography program at 8 p.m. Wednesday.
(...)
Several brokers and other experts offer pithy comments in “Wizards.” “Every generation thinks that the market can’t crash, things are different now, they say. But it always comes down, it’s just for different reasons,” says one.
 
Another says a bull market is like sex: “It feels best just before it ends.”
   
Google Books
The Wit & Wisdom of Wall Street
Edited by Bob Thomas
Dallas, TX: Bascom-Hall
2011
Pg. ?:
A bull market is like sex—when it feels best, it’s almost over.
 
Twitter   
Fibonaccing‏
@Bancotario
RT @WallStWitWisdom: “A bull market is like sex—when it feels best, it’s almost over.” HEHEHEHE….
4:52 PM - 27 Feb 2011
 
Twitter
Rajeev Thakkar‏
@RajeevThakkar
Warren Buffett’s letter: Remember the late Barton Biggs’s observation: “A bull market is like sex. It feels best just before it ends.”
8:03 AM - 24 Feb 2014
 
The Telegraph (London, UK)
Warren Buffett: Markets are like sex
Billionaire Warren Buffett quotes late money manager Barton Biggs in advice for new investors
By Andrew Trotman
5:15PM GMT 26 Feb 2014
There’s nothing like getting a big bang for your buck, and no one knows that more than billionaire investor Warren Buffett.
 
The 83-year-old founder of Berkshire Hathaway, whose investments have consistently beaten the stock market over the past 50 years, shared a few tips in this year’s annual letter to shareholders, including comparing the stock market with sex.
 
Mr Buffett said new investors tend to buy shares when the markets are rising and optimism is high, only to get disillusioned when prices fall.
 
Quoting the late money manager Barton Biggs, whose attention to emerging markets in the 1980s marked him as one of the world’s first and foremost global investment strategists, Mr Buffett added: “A bull market is like sex. It feels best just before it ends.”
 
Zero Hedge
Kass: “Investors Seemingly Learned Nothing From History”
by Tyler Durden
Sep 28, 2017 12:11 PM
Authored by Doug Kass via RealInvestmentAdvice.com,
“‘A bull market is like sex. It feels best just before it ends.’” – Warren Buffett
 
Twitter
Kester‏
@KesterWong
“‘A bull market is like sex. It feels best just before it ends.’” – Warren Buffett
How does a bear market feel like then? Me wonder
8:52 PM - 28 Sep 2017