You must always know when to pull out. A businessman isn't a mathematician. Remember that. Never become hypnotized by the beauty of numbers. A businessman is someone who buys at ten and is happy to get out at twelve. The other kind of man buys at ten, sees it rise to eighteen and does nothing. He is waiting for it to get to twenty. The beauty of numbers. When it drops to ten again he waits for it to get back to eighteen. When it drops to two he waits for it to get back to ten. Well, it gets back there. But he has wasted a quarter of his life. And all he's got out of his money is a little mathematical excitement.
- V.S. Naipaul, "A Bend in the River".