“Everything I need to know… I learned in kindergarten.”

All I Really Need to Know I Learned in Kindergarten (1986)
Context: All I really need to know about how to live and what to do and how to be, I learned in kindergarten. Wisdom was not at the top of the graduate-school mountain, but there in the sand pile at Sunday School. These are the things I learned. These are the things you already know:

Comment about the title of Robert Fulghum's famous book, in I'm Dysfunctional, You're Dysfunctional : The Recovery Movement and Other Self-Help Fashions (1992), Introduction, p. 7

Comparing his work as an international diplomat to that of his wife, Aida Elkachef, a kindergarten teacher, with a mention of the book by Robert Fulghum.
Breaking the Cycle (2003)

Source: The Search

Source: A Widow for One Year (1998), part II, ch. 7

Source: The Alchemist

Source: Still Writing: The Perils and Pleasures of a Creative Life

As quoted in "Republican conference: Day two - Bush 'proud' of family" http://www.bbc.com/news/world-us-canada-32850481 (22 May 2015), by Anthony Zurcher, BBC News, United Kingdom: British Broadcasting Corporation
2010s

Letter to Emily Holmes Coleman (2 February 1934) http://www.case.edu/artsci/engl/VSALM/mod/brandelmcdaniel/index/library.htm