Investors often fall in love with stocks that increase in value or pay good dividends. “Never fall in love with a stock” is a Wall Street adage cited in print from at least the 1950s. When a stock ceases to perform well, investors must be quick to fall out of “love” and to sell the stock.
 
“Marriage” often follows “love.” By at least the early 1960s, investors were being warned: “Don’t get married to a stock.”
   
     
7 August 1953, Oakland (CA) Tribune, “Women ‘Just Not Smart’ as Investors” by Dorothy Roe (AP Women’s Editor), pg. 9, col. 5:
2—Don’t fall in love with a stock. If it lets you down, get rid of it. No wise investor ever puts his securities away and forgets about them. Intelligent investing involves a knowledge of when to sell as well as when to buy.
 
21 June 1960, Logansport (IN) Pharos-Tribune, pg. 4, col. 6:
(By dancer Nicolas Darvas, author of “How I Made $2,000,000 in the Stock Market”—published by the American Research Council.)
(...)
I knew I must not fall in love with any stock when it rose or get angry when it fell…There are no such animals as good or bad stocks; there are only rising and falling stocks and I should hold the rising ones and sell those that fell.
   
16 April 1973, Greeley (MO) Tribune, “Trading rules offered” by Judith O. Rhoades, pg. A32, col. 5: 
No. 1, approach the situation without emotion. In other words, do not fall in love with a stock.
 
Google Books
Investment Analysis & Management
By Seww-Hock Saw and Choo Peng Lim
Published by Longman Singapore Publishers, 1990
Pg. 64:
Knowledgeable brokers teach their clients not to fall in love with a stock per se but to understand that changing one piece of paper for another may provide ...
   
Google Books
Beating the Street:
The Best-selling Author of One Up on Wall Street Shows You how to Pick Winning Stocks and Develop a Strategy for Mutual Funds
By Peter Lynch
New York, NY: Simon and Schuster
1994
Pg. 32:
Never fall in love with a stock; always have an open mind.
   
Google Groups: misc.invest.stocks
Newsgroups: misc.invest.stocks
From: “Gary Shannon”

Date: 1999/12/04
Subject: Re: Best of both worlds
   
They say you should never fall in love with a stock.  Well, I’m in love with all my stocks.  I’m familiar and comfortable with them.  They’ve made money for me and I understand their personalities.  They are my friends, my buddies.  That’s how close I need to feel to a stock before I’ll trade it. If you’re feeling grumpy you might put on a smile and fool a stranger, but your phoney smile will never fool a close friend.  And when one of my stocks is feeling frisky, or feeling grumpy, it can’t fool me either.  I know them too well.
   
Google Books
What’s Your Net Worth:
Click Your Way To Wealth
By Jennifer Openshaw
New York, NY: Basic Books
2002
Pg. 143:
Remember the Wall Street adage: never fall in love with a stock.
   
Access My Library
Don’t Fall In Love With A Stock.
Publication: Investor’s Business Daily
Publication Date: 14-MAY-02
Byline: CHRISTINA WISE
Investor Psychology: Third In A Series
Falling in love can be wonderful. There’s an extra bounce in your step, the sky seems a little more blue, the air a little more sweet.
 
But if the object of your affection is a stock, you’re in for heartbreak sooner or later.
 
It’s easy to grow attached to a stock, particularly one that’s made…
   
Google Books
Buy the Rumor, Sell the Fact:
85 Maxims of Wall Street and What They Really Mean
By Michael Maiello
Published by McGraw-Hill Professional
2004
Pg. 95:
Never Fall in Love with Horses or Stocks
     
Google Finance: Discussions for Apple Inc.
Lesson learned : Never ever fall in love with a stock
From:  .(JavaScript must be enabled to view this email address) - view profile
Date:  Wed, Jan 23 2008 1:02 pm
Email:  .(JavaScript must be enabled to view this email address)
   
Enough said.
         
FlayJot
4 Things People Forget About Owning Stocks.
By FlayJot ⋅ September 17, 2008
(...)
Stocks are Unemotional. The stock you own will act of its own accord, without concern for your feelings about the stock or underlying company.  The market doesn’t care about you, and you should keep this in mind when an investment becomes unfit for your portfolio.  Take heed of an old saying; “Never fall in love with a stock.”