If you take a look at my net worth, obviously I haven't received any good advice. But I've always admired Commodore Vanderbilt's advice to a young, earnest reporter: "Don't buy anything you don't want or sell anything you ain't got."
Vanderbilt was warning against speculation; he followed his own advice and died the richest self-made man in the world. I've never been an active trader - I don't have the personality for it - but Vanderbilt's advice is wonderful.
NEXT: Money doesn't make you happy