"If the probability of something happening is very small, then once it does happen, the consequences are bound to be catastrophic." Although this statement seems very out of place in the recent market, what the top student wants to say is that unpleasant words always appear when the crowd is at its loudest. The sharp rises and falls in U.S. stocks over the past two years are hard to predict at their turning points, but the magnitude of the decline after the turning point is surprisingly consistent. Especially during a continuous rally, the accumulated trading risk grows larger and larger. It's hard for us to predict when a decline will occur during an uptrend, but once it does, how should we hedge the risk in advance? Rather than losing sleep at high levels...