Not adapting my trading to the market conditions. I traded in an eSignal demo account for over a year and the results were very favorable. I started trading live in November and couldn't figure out why I was losing. I know the execution speed at times will be an issue but even factoring that in there was something else that was impacting my success. This was right when the sub prime mess was constantly talked about on CNBC. Suddenly the market (for me) was too volatile. I would be getting the direction of the stock correct but due to the whipsaw action I was experiencing too much of the pain of a losing trade (so I would get out) only to watch the stock move in my favor with me on the sidelines nursing a $500 loss.... The solution: decrease the share size to be able to tolerate the pain of the trade going against me until it moved in my favor. Its a lot easier holding on to a trade that is down $200 than $500. It did help my psyche to hear on CNBC one of the commentators say that there were traders on the floor of the NYSE with 30 years experience that didn't know what was going on with this market and that they were confused... If somebody with 30 years of real floor experience can't tell what is going on how could I expect myself to... again trade smaller and less until the market becomes more predictable...