The following graph shows that after some ups and downs the S&P 500 (American stock market) is exactly where it was on December 31, 1998. 12 years ago.
An investor who has patiently put money into this market over this period has earned exactly zero on stock appreciation.
It shows the importance of understanding long term cycles in markets. We are currently in a long term bear market in stocks and a long term bull market in commodities. Both cycles, which began in the year 2000, are secular and tend to last 15 - 20 years historically.
Stock price increases are good opportunities to sell (or go short) and commodity pull backs are good opportunities to purchase.