Apparent Contradictions,... Unfair?

My 3 year old daughter says, "But Daddy...You're drinking that juice out of my cup!", as I lethargically grab for a morning juice glass pre coffee downing time.
"Why, you're right. Isn't that something", I reply very matter of fact -- not in a way that insinuated any type of wrong doing whatsoever. I could hear however, the slight injustice in her voice, but I didn't respond to it. I can hear her thinking and recalling the talks that her mother and I have had with her about 'asking' to borrow people's things before we command use of them. Oh yes, well there's that, but this is just a little plastic glass, I think to myself. Three year olds do not yet know the natural variance that rules have or the Carte Blanche allowances of the big people, but we are soon to have those lengthy, Very Oft repeated discussions about the 'ins' and 'outs' of family law as it pertains to those who are less than 18 years of age and/or still live at home. ...And I am Certain that I have Things To Learn in the Process.