“The range of what we think and do is limited by what we fail to notice. And because we fail to notice that we fail to notice there is little we can do to change until we notice how failing to notice shapes our thoughts and deeds.”

Source: The Salmon of Doubt

TV Series and Specials (Includes DVDs), Trick of the Mind (2004–2006)

Canto IV, line 9 (tr. Mandelbaum).
The Divine Comedy (c. 1308–1321), Purgatorio

Source: The Peter Principle (1969), p. 20 cited in: James Ike Schaap (2011) " The Peter Principle: Is This Forty-Year-Old Universal Phenomenon in Decline or Growing? http://www.jgbm.org/page/1%20James%20Ike%20Schaap%20.pdf"

Source: The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory

Address to his branch and flight control team on the Monday morning following the Apollo 1 disaster (30 January 1967), known as "The Kranz Dictum"; as published in Failure Is Not An Option : Mission Control from Mercury to Apollo 13 and Beyond (2000) by Gene Kranz, p. 204. The phrase "tough and competent" was echoed by NASA Director Sean O'Keefe following the Space Shuttle Columbia disaster, adding that "these words are the price of admission to the ranks of NASA, and we should adopt it that way."
Context: Spaceflight will never tolerate carelessness, incapacity, and neglect. Somewhere, somehow, we screwed up. It could have been in design, build, or test. Whatever it was, we should have caught it.
We were too gung ho about the schedule and we locked out all of the problems we saw each day in our work. Every element of the program was in trouble and so were we. The simulators were not working, Mission Control was behind in virtually every area, and the flight and test procedures changed daily. Nothing we did had any shelf life. Not one of us stood up and said, "Dammit, stop!"
I don't know what Thompson's committee will find as the cause, but I know what I find. We are the cause! We were not ready! We did not do our job. We were rolling the dice, hoping that things would come together by launch day, when in our hearts we knew it would take a miracle. We were pushing the schedule and betting that the Cape would slip before we did.
From this day forward, Flight Control will be known by two words: "Tough and Competent." Tough means we are forever accountable for what we do or what we fail to do. We will never again compromise our responsibilities. Every time we walk into Mission Control we will know what we stand for.
Competent means we will never take anything for granted. We will never be found short in our knowledge and in our skills. Mission Control will be perfect.
When you leave this meeting today you will go to your office and the first thing you will do there is to write "Tough and Competent" on your blackboards. It will never be erased. Each day when you enter the room these words will remind you of the price paid by Grissom, White, and Chaffee. These words are the price of admission to the ranks of Mission Control.

1960, The New Frontier
Context: For the harsh facts of the matter are that we stand on this frontier at a turning-point in history. We must prove all over again whether this nation — or any nation so conceived — can long endure — whether our society — with its freedom of choice, its breadth of opportunity, its range of alternatives — can compete with the single-minded advance of the Communist system. Can a nation organized and governed such as ours endure? That is the real question. Have we the nerve and the will? Can we carry through in an age where we will witness not only new breakthroughs in weapons of destruction — but also a race for mastery of the sky and the rain, the ocean and the tides, the far side of space and the inside of men's minds? Are we up to the task — are we equal to the challenge? Are we willing to match the Russian sacrifice of the present for the future — or must we sacrifice our future in order to enjoy the present? That is the question of the New Frontier. That is the choice our nation must make — a choice that lies not merely between two men or two parties, but between the public interest and private comfort — between national greatness and national decline — between the fresh air of progress and the stale, dank atmosphere of "normalcy" — between determined dedication and creeping mediocrity. All mankind waits upon our decision. A whole world looks to see what we will do. We cannot fail their trust, we cannot fail to try.