A classic mistake, made by new traders, including smart ones, is to get all excited about results from paper trading or demo trading, which did not realistically take into account the costs of executing transactions. These costs include such things as commissions, spreads, slippage, front-running, stop-running, re-quoting, man-quoting, shading, individualized pricing, anti-picking rules, freezing, etc., etc. The new trader almost always finds that the strategy which worked on paper either fails to cover the transaction costs of real trading, or it was based on temporary market conditions which quickly disappear and leave the strategy a loser.