The 3 principles serve as guides and a vehicle for reflection. It's my belief that they are appropriate principles within a D/s relationship and that they work well regardless of whether you are a Mistress or a slave. Several years after putting these principles into effect, I still find layers of meaning that I can apply to my personal affairs.
Looking more deeply, one discovers that accepting gifts with two hands demands that one actually _recognize_ the amazing gifts one receives on a regular basis.
Please and thank you demands that one actively look for opportunities to be grateful. "Grace" means "thanks". Thus "full of grace" and "full of thanks" are the same thing.
"Make me proud" is (as you seem to be discovering) deceptively simple. Inherent in this command is everything that one needs to know about serving one's Mistress. It's also a reminder of my duty as a Dominant: that pride of ownership is not based only on passive acts... It's something I make.
Lady Nichola