People affected by Mr. Market

In 1999, People fear they made less money than someone else: They feared that they would bump into somebody at a BBQ who was getting even richer even quicker by day trading dot.com stocks than they were.

By 2003, they feared that the stock market might keep dropping until it wiped out whatever traces of wealth you still had left.  So, they sold all of the stocks.

The people who take the biggest gambles and make the biggest gains in a bull market are almost always the ones who get hurt the worst in the bear market that inevitably follow. (Being "right" makes speculators even more eager to take extra risk, as their confidence catches fire.