I just watched this movie again (I originally saw it about a year after it came out) and it really is driving me crazy that they make a big deal of these three rules and never reveal the third. I'm sure it's on purpose and it's for the mother's POV that she didn't last long enough to even hear the third one. The first rule is no red meat. The second is no refined sugar. And then he says, "The third one is going to drive you crazy. You're not going to like it. The other two are easy compared to this." I just want to make sure I didn't miss anything.
Such an intense and depressing movie, but really artistically beautiful and well done.