“Be happy with what you have while working for what you want” is a saying that has been printed on many images. “Be happy with what you have while working toward getting what you want” was printed in many horoscope columns in January and February 1978, but this use might have be coincidental.
 
“Be happy with what you have while working for what you want” was printed in the book Life’s Little Instruction Book: 511 Reminders for a Happy and Rewarding Life (1991) by H. Jackson Brown. Brown was usually cited as the author.
 
“Be happy with what you have while working for what you want. Helen Keller” was posted on Twitter by PatB on July 8, 2009. There is no evidence that American author and political activist Helen Keller (1880-1968) ever said this, but she has been frequently credited (since at least 2009) as the author.
   
       
Wikipedia: H. Jackson Brown Jr.
Harriett Jackson Brown Jr. is an American author best known for his inspirational book, Life’s Little Instruction Book, which was a New York Times bestseller (1991–1994). Its sequel Life’s Little Instruction Book: Volume 2 also made it to the same best seller list in 1993.
 
20 January 1978, The Press-Tribune (Roseville, CA), “Horoscope,” pg. 10, col. 5: 
GEMINI (...) Be happy with what you have while working toward getting what you want.
 
Google Books
Life’s Little Instruction Book:
511 Reminders for a Happy and Rewarding Life
By H. Jackson Brown
Nashville, TN: Rutledge Hill Press
1991
Pg. ?:
1166 Be happy with what you have while working for what you want.
           
22 January 1996, The Sun (London, UK), “Until the kids move out of your house, don’t buy anything suede” by Caroline Graham, pg. 22:
PROUD Dad H. Jackson Brown compiled a list of funny, touching and useful sayings to guide his son Adam through life. And when he turned his fatherly advice into Life’s Little Instruction Book it took America by storm.
(...)
Be happy with what you have while working for what you want.
     
Google Groups: Work911 Forum
Nov. 14, 2005 Work 911 Workplace Newsletter
Robert Bacal
4/5/06
(...)
Quote of the Week
“Be happy with what you have while working for what you want.”
~~H. Jackson Brown
The Complete Life’s Little Instruction Book
 
Twitter 
PatB
@BeautyOfWellnes
Be happy with what you have while working for what you want. Helen Keller
5:43 AM - 8 Jul 2009
 
Elite Daily
24 Quotes About Being Thankful That Are Perfect For Your Holiday Snaps, Because #BlessUp
BY RACHEL CHAPMAN
NOV 7 2017
(...)
11. “Be happy with what you have while working for what you want.” — Helen Keller
     
Refinery29 
The Most Inspiring Gratitude Quotes To Share On Instagram This Thanksgiving
LUDMILA LEIVA
NOVEMBER 19, 2018, 12:00 PM
(...)
8. ‘Be happy with what you have while working for what you want.’ — Helen Keller
 
YourTango
50 New Year’s Resolutions To Live By In 2019
Mehruba Chowdhury
December 18, 2018
(...)
5. Don’t forget to be happy with what you have.
“Be happy with what you have while working for what you want.” —​ Unknown
 
YourTango
50 Motivating Life Quotes For People Who Can’t Stand Sappy Quotes
Kayla Kibbe
May 5, 2019
(...)
20. Be happy now.
“Be happy with what you have while working for what you want.” — Unknown