Fighting off Mush

I recently adopted a new parenting strategy - when Kate asks me "why" she can or can't do something, I've started giving her the actual reason versus just saying "because." I'm happy to report that it seems to be working, as she's submitting more easily. A specific example is, when she asks to watch TV and I tell her no, I've explained it's because "if you watch too much TV your brain will turn to mush." Now she nods and moves on to something else. Here is a funny example from today of what this strategy is producing:

Kate: "Mommy, can I have another cookie."
Me: "No"
Kate: "But Mommy, I really want another cookie."
Me: "I understand you want another cookie. I would like another one too. But we can only have one cookie."
Kate: "Because our brain's will turn to mush."
Me: "No, if you eat to many cookies, your belly turns to mush, not your brain."
Kate: "And we don't want a mush brain or a mush belly."
Me: "That's exactly right, Kate."