Yes, once - many, many years ago. I thought I had made a wrong decision. Of course, it turned out that I had been right all along. But I was wrong to have thought that I was wrong.
Source: Facing the Music, by H. Temianka.
-- John Foster Dulles, (Feb 25 1888-1959), US government official; He was secretary of state, 1953-59, under President Eisenhower; architect of many major elements of U.S. foreign policy in the Cold War.