“Suffering. That was the key.”
Liddy, G. Gordon, Will: The Autobiography of G. Gordon Liddy (St. Martin's Press 1980), pg. 12 https://books.google.com/books?id=YRty_4HT_8kC&pg=PA12&lpg=PA12&dq=liddy+Suffering.+That+was+the+key&source=bl&ots=RZK5OAAlFM&sig=xc-5y539aH5ERGbwmGwvfi-I0wY&hl=en&sa=X&ved=2ahUKEwidzYmrg5jeAhWxHTQIHf5_DoIQ6AEwBHoECAYQAQ#v=onepage&q=liddy%20Suffering.%20That%20was%20the%20key&f=false, describing his epiphany about how to conquer fear.
Compare the fictional reply, attributed to Liddy in All the President's Men (1976), when asked how he could keep his hand over a lit candle until his flesh seared: "The trick is not minding."
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G. Gordon Liddy 5
American lawyer in Watergate scandal 1930Related quotes

Quote in his letter to brother Theo, from Arles, France, 9 March. 1889; as quoted in Vincent van Gogh, edited by Alfred H. Barr; Museum of Modern Art, New York, 1935 https://www.moma.org/documents/moma_catalogue_1996_300061887.pdf, (letter 579), p 25
1880s, 1889

Thoughts and Aphorisms (1913), Bhakti

“Innovation is the key to the future, but basic research is the key to future innovation.”
"Will Innovation Flourish in the Future?," 2002

“I don't know the key to success, but the key to failure is trying to please everybody.”
Originally from Herbert Bayard Swope (1882-1958); often attributed to Cosby, he actually cites this as a sound advice he once read elsewhere, in "Dr. Bill Cosby" in Ebony, Vol. 32, No. 8 (June 1977), p. 136
Misattributed
On the Economic Partnership Agreement (EPA), in Will Ross, " Africans wary of Europe's trade offer http://news.bbc.co.uk/2/hi/africa/7134407.stm", BBC (8 December, 2007).

Vegn vos Firn op fun Yidishkeit, 1911. S. Liptzin. Peretz. Yivo, 1947, p. 372.
Context: They are all so-called Christian nations, but... this superimposed religion... does not penetrate into the core of their souls. It has no relation to their daily experience... It is a key to open a heaven after death and not a key with which to force open the portals of this life.