Its really not good when we let the minus floating and if there is less amount in our balance . i had an experience many days ago when aud/usd naturally not traded (most of the time ) high of 1.000 and that time i was newbie. i open a position of sell order and its go higher and higher and cross 1.000 , i deposit more money but atlast i lost all. so i think its always good to use SL.