I have learned one thing while writing my trading program. The success of any set of parameters depends on the underlying security -- stock in my case. How do you decide whether the system legitimately works for a particular stock. More importantly, how do you tell that the system no longer works for the stock? I have trying various strategies with the equity curve. In effect, I was "trading" the EC. When it goes up, trade the system. When it goes down, don't trade. But, when the equity curve is choppy, it is extremely difficult to decide whether to trade or not. I would love to hear what the experienced traders will say about this.