i understand the basic principles behind muscle building, but am curious to know when you have lifted enough for that particular session. I work to failure on all muscle groups with long rests in between 1-2mins using heavy dumbells. However if i rest long enough i can always pull out another set and this could go on all night if i wanted to. I guess what i'm trying to say is when do you know when to stop? i know its a silly one but how do the rest of you feel after training? and when do u say to yourselves enough is enough? 