“The act of concentrating on a given subject is, conversely, the act of temporarily forgetting everything else. This is one reason why, in most cases, highly successful people seem to be possessed of great calm and impressive reserves of energy. Capable of intense concentration on basic questions, they are not worn down by superficial difficulties, distracting side issues or the enervating friction of a divided mind. Professionally hard at work, they are psychologically on vacation: this is one case where conventional acheivement is completely in accord with mental and physical health.”

Robert Grudin, Time And The Art Of Living (Page 106)