It has been said that there is no fool like an old fool, except a young fool. But the young fool has first to grow up to be an old fool to realize what a damn fool he was when he was a young fool.
Source: In The Ultimate Success Quotations Library, 1997.
-- Harold Macmillan, (Feb 10 1894-1986), English politician; He was prime minister from January 1957 to October 1963.