One, which I mention several times elsewhere, is the need for patience if big profits are to be made from investment. Put another way, it is often easier to tell what will happen to the price of a stock than how much time will elapse before it happens. The other is the inherently deceptive nature of the stock market. Doing what everybody else is doing at the moment, and therefore what you have an almost irresistible urge to do, is often the wrong thing to do at all.