That is right because without calculating the %s of the wins or losses, a trader will not have a clear insight of his ongoing trading journey and he will not know where to take maximum profits to beat the losses and where to take the least loss if profit is not being seen in that trade. A good trader must diversify his capital in different trades and can also use his full capital but with proper risk management, so if there are 10 open trades of equal amounts and 7 of them are in profits, that trader should take those profits at times when it is needed. If 3 of those trades are in losses, trader should have set a good SL to let him save himself from losing big from those trades.