The American economy is going to do fine. But it won't do fine every year and every week and every month. I mean, if you don't believe that, forget about buying stocks anyway. But it stands to reason. I mean, we get more productive every year, you know. It's a positive-sum game, long term. And the only way an investor can get killed is by high fees or by trying to outsmart the market. NEXT: Are the U.S. financial markets losing their edge?