Quote from praetorian2:
My opinion is that most traders fail because they are undercapitalized. I have seen many people who give up when they get very near to the breakeven point b/c they have nothing left for the final push to breakeven.
Second largest reason is just that most traders come into the game without any real knowlege of how they will trade or what system they'll use. Buying something in motion and hoping it stays in motion is not enough to make you profitable in the long term.
Third largest reason is that someone doesn't follow his system, but dabbles in other systems that seem hot at the moment. If a system has had good results in the most recent time period, most likely, it's period of outperformance is just about over. Chasing what's hot is almost doomed to failure.
Fourth, most people think that trading is something you can do for 20 minutes a week. I know a lot of very profitable traders. Most of them are online and doing research at 3am on a saturday night. In fact, I often drop ideas on them at around that time. This is the reason for their success. They are a slave to their trading. If you don't intend to be that dedicated, just write a check to me. It will save me the commission costs. Trading isn't an effortless get rich plan.
The final reason is just sheer stupidity. Lets face it, 95% of all traders fail. I'd say that about 95% of the population is completely retarded. I think there's a similarity in the two statistics. Some people just lack the simple intelligence to trade profitably. Somehow most of these people seem to make it onto CNBC despite their best efforts to squander the retirement money entrusted to them.