‘You lay down rather severe rules for one who wishes to succeed in life,’ I ventured, ‘working eighteen hours a day.’‘

Not at all,’ he said. ‘You do something all day long, don’t you? Every one does. If you get up at seven o’clock and go to bed at eleven, you have put in sixteen good hours, and it is certain with most men, that they have been doing something all the time. They have been either walking, or reading, or writing, or thinking. The only trouble is that they do it about a great many things and I do it about one. If they took the time in question and applied it in one direction, to one object, they would succeed. SucceAss is sure to follow such application. The trouble lies in the fact that people do not have an object one thing to which they stick, letting all else go. Success is the product of the severest kind of mental and physical application.’

via Thomas Edison, Power-Napper: The Great Inventor on Sleep and Success | Brain Pickings.