Do adults have a real line between habits and superstitions?

My kids this week argued that the red crayon is ONLY for fire trucks and the blue one is ONLY for water, and you can't touch someone else's favorite spot on the rug during circle time. I keep their rules straight by calling them pretend, but I'm starting to wonder if my own 'I can't start grading until the coffee's in the exact same mug' is actually any different. Where do you draw that line for yourself, or do you even bother?