In Michael Covel’s book- Trend Following, the legendary trader John Henry is quoted as saying:

“We can’t always take advantage of a particular period. However, in an uncertain world, perhaps the investment philosophy that makes the most sense, if you study the implications carefully, is trend following. Trend following consists of buying high and selling low. For 19 years, we have consistently bought high and sold low. If trends were not the underlying nature of markets, our type of trading would have very quickly put us out of business. It would not take 19 years or even 19 months of buying high or selling low ALL of the time to bankrupt you.

Nevertheless, trends are an integral, underlying reality in life. How can someone buy high, sell low, and be successful for two decades unless the underlying nature of markets is to trend? On the other hand I’ve seen year after year, brilliant men buying low and selling high for awhile successfully and then going broke because they thought they understood why a certain investment instrument had to perform in accordance to their personal logic.”