For slaves, our obedience determines what can be enjoyed. It gives us our self esteem and pleasure. It connects us. It gives us purpose. It validates us. i have come to believe that obedience is the very spirit of slavery; it is the special charisma of slave creatures. Obedience is the structural steel of our slave identity, and the spine of the slave's conviction. Obedience alone determines what is right and what is wrong. It frees a slave to be what only a slave can be- one whose will has been replaced by that of another. Obedience is usually the single most important concern of a slave, and this frees us from almost all other concerns. It is the overarching principle through which right and wrong is assessed by us, and by Those we serve.
The slave asks himself only, "Did I obey?" If the answer is "yes", then he did everything he could or should do. If the answer is no, then, at best, he did nothing worth noting. At worst, he was disobedient and perhaps even insolent.
While some of this may be hyperbolic fantasy (ie. the slave's will being replaced entirely by another's is just not happening to most of us, I am betting, except in limited doses), for me realizing the core of what the author is saying IS liberating.
Say I feel guilt for not doing something I think I ought to do, but then Master says "I order you" not to do that thing. I have obeyed him, so why should I feel guilty for not doing something I was ordered not to do? I can't anymore, because obedience is the main thing, not doing what I think I ought.
It is freeing.
If my orders for the day were A, B and C, and I did those things, I don't feel guilty for not doing D, E and F as well.
It takes away some of the wondering and doubt.