You must know all there is to know in your particular field and keep on the alert for new knowledge. The least difference in knowledge between you and another man may spell his success and your failure.
Henry FordNone of our men are 'experts.' We have most unfortunately found it necessary to get rid of a man as soon as he thinks himself an expert because no one ever considers himself expert if he really knows his job... Thinking always ahead, thinking always of trying to do more, brings a state of mind in which nothing is impossible.
Henry Ford