The “Dear Abby” syndicated newspaper advice column by Abigail Van Buren (the pen name, written by Pauline Phillips and her daughter Jeanine Phillips) in February 1991 answered a letter from “Love Starved,” who was happily married but wanted something more. Abby’s advice was:
 
“As my sainted grandmother used to say, ‘Don’t throw away cake to start looking for crumbs.’”
 
If this was from the grandmother of Pauline Phillips (1918-2013), the saying must have been in existence in the 1800s. “Cake” means something big, and “crumbs” means something small. Unfortunately, other print citations of the saying have not been found.
 
“Looking/Reaching for crumbs” is sometimes given first in the expression. “Quit reaching for crumbs, when there’s cake right in front of you. #GodIsBetter” was posted on Twitter by Aubrey Thompson on October 2, 2014. (The “cake” is God/heaven.) “You’re too busy looking for crumbs when there’s a cake in front of you” was posted on Twitter by Seth the Asian on October 13, 2014.
 
   
Wikipedia: Dear Abby
Dear Abby is an American advice column founded in 1956 by Pauline Phillips under the pen name “Abigail Van Buren” and carried on today by her daughter, Jeanne Phillips, who now owns the legal rights to the pen name.
(...)
Pauline Phillips wrote the column herself until 1987, at which time her daughter Jeanne Phillips began writing the column with her.
 
Newspapers.com
13 February 1991, The Arizona Daily Star (Tucson, AZ), “Dear Abby: Don’t toss away cake to start looking for crumbs” by Abigail Van Buren, pg. C4, col. 2:
As my sainted grandmother used to say, “Don’t throw away cake to start looking for crumbs.”
 
Newspapers.com
16 February 1991, Indiana (PA) Gazette, “Dear Abby” advice column by Abigail Van Buren, Family Leisure sec., pg. 23, col. 1:
As my sainted grandmother used to say, “Don’t throw away cake to start looking for crumbs.”
         
Twitter
Aubrey Thompson
@Swo131
Quit reaching for crumbs, when there’s cake right in front of you. #GodIsBetter
5:31 PM · Oct 2, 2014·Twitter Web Client
 
Twitter
Seth the Asian
@SethTheAsian
You’re too busy looking for crumbs when there’s a cake in front of you
5:06 PM · Oct 13, 2014·Twitter for iPhone
   
Twitter
Ke$afoda
@KSFUD
You’re reaching for crumbs,when there’s cake right in front of you! http://fb.me/7jBvNYn9V
7:01 PM · May 24, 2015·Facebook
 
Twitter
Mariam Al Saie
@MariamAlSaie
Don’t look for crumbs when there’s a huge cake in front of you.
1:38 PM · Jun 1, 2015·Twitter for iPhone
   
Twitter
Will Neff
@WillENeffSaid
Don’t look for crumbs when there’s a cake right in front of you!
10:13 AM · Jul 27, 2015·Buffer
   
Twitter
Vahldra
@Vahldra
“Stop looking for crumbs when there’s a cake right in front of you”—Irony? pot meet kettle.
6:15 PM · Sep 20, 2016·Twitter Web Client
 
Twitter
majorkeysbeats.com
@Major_Keys
I was looking for crumbs when God had the whole cake waiting for me!
1:20 PM · Feb 5, 2018·Twitter for Android
 
Twitter
🇺🇸🇺🇸🇺🇸
@ruffdood
Replying to @CNNPolitics
Mueller looking for crumbs when there’s a whole cake of lies with Hillary and her campaign😂😂😂. Democrat idiots
10:09 AM · Feb 20, 2018·Twitter for iPhone
 
Quora (November 26, 2019)
Who came up with the saying “Don’t throw away the whole cake just to win a little crumb”, and what does it mean to you?