Eleanor Roosevelt said this quote

“ ...Learn to concentrate, to give all your attention to the thing at hand, and then to be able to put it aside and go on to the next thing without confusion. My husband said that being President of the United States meant that you saw more kinds of people, took up more subjects, and learn more about a variety of things than anyone else. But it required complete concentration on the person you were with and on what he was saying. When that person left the room, you pulled down a shade in your mind, and you were ready, with your attention free, for what the next person had to say. You might have to shift from banking to forestry, but each subject had the attention and concentration it required and each, in turn, was put in the back of the mind, ready to be called upon when needed. ”