It is those who concentrate on but one thing at a time who advance in this world. The great man or woman is the one who never steps outside his or her specialty or foolishly dissipates his or her individuality.
Source: In The Ultimate Success Quotations Library, 1997.
-- Og Mandino, (Dec 12 1923-1996), US editor, writer, motivational speaker; He is known for his success book TThe Greatest Salesman in the World which contains the ten timeless and time-tested principles of success.