You have two Masters that asked you the same question?? Just the logistics of that boggles my mind.
Unfortunately, I can't really help you in the slightest. In my relationship, refering to myself as a "worthless piece of shit" would result in some pretty serious punishment. Putting down my Master's property (i.e. me) is akin to insulting him outright. Definitely not a good idea.
So I wonder why they are asking this of you? Do they really want you to think that you are worthless? And what honour is it to them that their sub is a piece of shit? Maybe someone can explain this dynamic to me, because at the moment I really don't get it.