From a story on commentary.org by Andrew Roberts headlined “Paul Johnson: How a Serious Man Changed the World”:

When Paul Johnson was a schoolboy, he met Winston Churchill on the steps of the Clifton Arms public house in Lytham in Lancashire. The prime minister gave him one of the long matches that he used to light his cigars, emboldening young Paul to ask, “Mr. Churchill, sir, to what do you attribute your success in life?” The reply was instantaneous: “Conservation of energy. Never stand up when you can sit down. And never sit down when you can lie down.”