“You’re only as good as your last trade” is an old adage for traders on Wall Street, cited in print since at least 1987. It’s another version of the saying, “What have you done for me lately?”
 
The saying has appeared in many other industries. Humorist Will Rogers wrote in 1935 about Hollywood that “You are only as good as your last picture.” On Broadway, “You’re only as good as your last show.” In the music business, “You’re only as good as your last record.” In sports, “You’re only as good as your last game.” Wall Street’s version of “You’re only as good as your last trade” has had the popularity of the other versions.
 
 
21 July 1935, Miami (FL) Daily News-Record, “Will Rogers Says,” pg. 10, col. 3:
Say this running a Government is kinder like our movie business. You are only as good as your last picture.
   
Google Books
West of Wall Street
By George Angell and Barry Haigh
Chicago, IL: Longman Financial Services Pub.
1987, ©1988
Pg. 75:
One way to maintain your equilibrium under pressure is to remember that you are only as good as your last trade. No matter how much money you’ve made, you start anew each day at square one.
 
1 April 1996, Hartford (CT) Courant, “No title for Kentucky? Don’t even propose it” by Jeff Jacobs, pg. C1”
“My brother-in-law has an expression: `On Wall Street, you’re only as good as your last trade.’”
     
Google Books
Dynamic Hedging:
Managing vanilla and exotic options
By Nassim Taleb
New York, NY: Wiley
1996
Pg. 65:
In a long Wall Street career, I have often heard the adage: “You are as good as your last trade.” Often the behavior of the managers of traders is dictated by their latest run. Investors somehow are not as easily fooled.
 
Google Books
DeMark on Day Trading Options:
Using options to cash in on the day trading phenomenon
By Thomas R. DeMark
Boston, MA: McGraw Hill
1999
Pg. III:
You’ve heard the expressions “you’re only as good as your last trade,” “trading opportunities are like city buses — if you miss one, another will appear shortly,” and the ever-quoted market nemesis “coulda, woulda, shoulda.”
 
Red Herring
Will success spoil TheStreet.com?
13 May 1999, 22:00
(...)
It all comes back to that old Wall Street adage, “You’re only as good as your last trade.” For TheStreet.com, that was $60 a share.
   
Google Books
Rebound Rules LP:
The Art of Success 2.0
By Rick Pitino and Pat Forde
New York, NY: Harper Luxe
2008
Pg. 76:
In coaching, you’re only as good as your last game, and on Wall Street, you’re only as good as your last trade.
 
Google Books
The Sellout:
How Three Decades of Wall Street Greed and Government Mismanagement Destroyed the Global Financial System
By Charles Gasparino
New York, NY: Harper Business
2010, ©2009
Pg. 69:
On Wall Street you’re only as good as your last trade.