American business executive (and later politician) Herman Cain said in Parade Magazine in October 1996:
   
“Success is not the key to happiness. Happiness is the key to success. If you love what you are doing, you will be successful.”
   
German—and later French—theologian, organist, philosopher and physician Albert Schweitzer (1875-1965) has frequently been credited with the quotation since 2005, but Schweitzer never said it. The quote has been printed on many posters, with credit variously given to Herman Cain, Albert Schweitzer and Buddha.
 
Other sayings about the “key to success” include “I found the key to success, only to discover that the door was never locked,” “I looked for the key to success and then found it’s a combination lock,” “If you can’t find the key to success, pick the lock,” “Just when you find the key to the market, they change the locks” and “Successful pianists know the key to success.”
   
     
Wikipedia: Herman Cain
Herman Cain (born December 13, 1945) is an American author, business executive, radio host, syndicated columnist, and Tea Party activist from Georgia. He was a candidate for the 2012 U.S. Republican Party presidential nomination.
 
13 October 1996, Augusta (GA) Chronicle, “‘I Chose To Change My Life’ (Herman Cain—ed.)” by Wallace Terry, Parade Magazine, pg. 5, col. 3:
“One of the keys to success in business is being happy with what you are doing, no matter what you earn,” he continued. Success is not the key to happiness. Happiness is the key to success. If you love what you are doing, you will be successful.”
   
Google Books
Life’s Instructions for Wisdom, Success, and Happiness
By H. Jackson Brown
Nashville, TN: Rutledge Hill Press
2000
Pg. ?:
105. Remember that success is not the key to happiness—happiness is the key to success.
 
Google News Archive
22 July 2004, Glenville (WV) Democrat/Pathfinderpg. 8B, col. 5:
“Success is not the key to happiness. Happiness is the key to success. If you love what you are doing, you will be successful.”—Herman Cain
   
Google Books
How to Ace Your Way Through College—and Still Have a Life!:
101 Insider Secrets to Getting Good Grades for the Non-Geek
By David Kennedy
Broomfield, CO: Wellness Research Pub.
2005
Pg. 19:
The late author/theologian Albert Schweitzer said it best: Happiness is the key to success. If you love what you are doing, you will be successful.”
 
Google News Archive
13 January 2005, The Ledger (Lakeland, FL), pg. F4, col. 8:
They Said It
“Success is not the key to happiness. Happiness is the key to success.”
Albert Schweitzer
philosopher, physician, musician, Nobel laureate (1875-1965)
   
Fake Buddha Quotes
September 11, 2012
“Success is not the key to happiness; happiness is the key to success. If you love what you are doing, you will be successful.”
This one had been on my list (I have a backlog of over forty quotes to investigate) for some time, but Warren Adams-Ockrassa sent it to me, saying “This just sounds so much like a Zig Ziglar quote that it’s more or less impossible for me to imagine Gotama ever saying anything even remotely like it” and this prompted me to do some digging around. I shared Warren’s suspicion that it was from the 20th century self-help genre.
 
I’d actually started researching this quote a few weeks ago, and had found it mainly attributed to Albert Schweitzer, with a minority plumping for — wait for it — Herman Cain.
 
Twitter
Seven Quotes
‏@sevenquotes
Success is not the key to happiness. Happiness is the key to success. If you love what you are doing, you will be successful. #Schweitzer
2:13 AM - 29 Mar 2015