The investor's chief problem - and even his worst enemy - is likely to be himself.
Most businesses change in character and quality over the years, sometimes for the better, perhaps more often for the worse. The investor need not watch his companiesâ€™ performance like a hawk; but he should give it a good, hard look from time to time.
Most of the time common stocks are subject to irrational and excessive price fluctuations in both directions as the consequence of the ingrained tendency of most people to speculate or gamble... to give way to hope, fear and greed.
In the short run the market is a voting machine, but in the long run it is a weighing machine.