When a beginner puts on a trade too big for his account, and it starts to swing, it floods him with adrenaline. A upswing gives him enough money to dream about moving to easy street. Feeling elated, he misses the signals of a top and gets caught in a downside reversal. A downswing puts him into such a state of fear that he misses the signals of a bottom and sells out right near the lows. Beginners pay more attention to their emotions than to the reality of the markets.
– Alexander Elder, Come Into My Trading Room: A Complete Guide to Trading