One line that I've always hated is "Failure is not an option."
Rather, failure should always be considered carefully in strategic discussions. One question that needs to be asked is, "How could we lose this thing?" That helps sharpen the discussion and helps lead to distinctions between what is essential and what is merely important, as Eisenhower put it early in World War II.
I mention all this because Paul Kennedy mentions in The Rise and Fall of British Naval Mastery that early in the 7 Years' War (a.k.a. the French and Indian War), the British recognized early on that the only way they could totally lose was through a French invasion of England. So job one was to prevent that.
Thomas E. Ricks covered the U.S. military for the Washington Post from 2000 through 2008.