“All businesses operate below their true potential. That is unavoidable, given the fallibility of human beings.”

Transhumanism (1957)
Context: We are beginning to realize that even the most fortunate people are living far below capacity, and that most human beings develop not more than a small fraction of their potential mental and spiritual efficiency. The human race, in fact, is surrounded by a large area of unrealized possibilities, a challenge to the spirit of exploration.

Attributed to Mary Parker Follett in: Business: The Ultimate Resource, 2001. p. 904.
Attributed from postum publications

Letter to Benjamin Harrison V (9 March 1789), published in Washington's Writings: Being His Correspondence, Addresses, Messages, and Other Papers, Official and Private, Selected and Published from the Original Manuscripts https://play.google.com/store/books/details?id=DTlEAQAAMAAJ&rdid=book-DTlEAQAAMAAJ&rdot=1, Volume IX, p. 475.
1780s

Books, Confessions of a Conjuror (2010)

Attributed to Follett in: Richard C. Wallace, ‎David E. Engel, ‎Dr. James E. Mooney (1997). The learning school: a guide to vision-based leadership. p. ix
Attributed from postum publications

Un estado totalitario armonizará en España el funcionamiento de todas las capacidades y energías del país, que dentro de la Unidad Nacional, el trabajo estimado como el más ineludible de los deberes será el único exponente de la voluntad popular.
Victory speech in Madrid (19 May 1939), quoted in Espana Nuevo Siglo‎ (1997) by Tim Connell and Juan Kattán-Ibarra, p. 174

Part I : Contemporary Issues in Science, Ch. 1 : "The Scientist as Rebel"; this first appeared in New York Review of Books (25 May 1995).
The Scientist As Rebel (2006)
Context: There is no such thing as a unique scientific vision, any more than there is a unique poetic vision. Science is a mosaic of partial and conflicting visions. But there is one common element in these visions. The common element is rebellion against the restrictions imposed by the locally prevailing culture, Western or Eastern as the case may be. It is no more Western than it is Arab or Indian or Japanese or Chinese. Arabs and Indians and Japanese and Chinese had a big share in the development of modern science. And two thousand years earlier, the beginnings of science were as much Babylonian and Egyptian as Greek. One of the central facts about science is that it pays no attention to East and West and North and South and black and yellow and white. It belongs to everybody who is willing to make the effort to learn it. And what is true of science is true of poetry.... Poetry and science are gifts given to all of humanity.

Source: They Fight Like Soldiers, They Die Like Children: The Global Quest to Eradicate the Use of Child Soldiers

Variant: You are never given a dream without also being given the power to make it true. You may have to work for it, however.
Source: Illusions: The Adventures of a Reluctant Messiah