The average doctor may be more likely than the average widow to elect to become an enterprising investor, and he is perhaps more likely to succeed in the undertaking. He has one important handicap, however―the fact that he has less time available to give to his investment education and to the administration of his funds. In fact, medical men have been notoriously unsuccessful in their security dealings. The reason for this is that they usually have an ample confidence in their own intelligence and a strong desire to make a good return on their money, without the realization that to do so successfully requires both considerable attention to the matter and something of a professional approach to security values.
―The Intelligent Investor, Chapter 5