Actually Bank Trader have get a Big Capital and they're open the Lot Volume in a small amount because they have a strictly rules of thumbs For one open position they cannot get a loss more then 2% from the Balance and secondly if that day they already get loss 10 times from their 10 trades they must quit from trade for the day and will continue to trade again for tomorrow so in one day they only tolerate loss not more then the 20% from their big capital.