I sit here all day trying to persuade people to do the things they ought to have sense enough to do without my persuading them

From Obituary - Richard Neustadt.  The subheading is Richard Neustadt, adviser to presidents, died on October 31st, aged 84.  The Economist Nov 13th 2003.

The year was 1952, with Dwight Eisenhower about to trounce Adlai Stevenson, and Harry Truman, the Oval Office incumbent, was in bitter mood. “He'll sit here,” he said, drumming his fingers on the desk, “and he'll say, ‘Do this!' ‘Do that!' And nothing will happen. Poor Ike—it won't be a bit like the army.”

Had he himself done any better? Alas, no. “I sit here all day trying to persuade people to do the things they ought to have sense enough to do without my persuading them...That's all the powers of the president amount to.”