It's a paradigm thing: if you're looking, in a rule, for the best possible approximation of a sophisticated reality, then you'll spend time calibrating for that, and that's fine. That's not what I'm looking at here.
My interest is behavior, specifically, changing behavior and habit, which is some of the most difficult kind of change we can, and need, to put ourselves through.
Fast, almost arbitrary, simple, clear, iron clad, zero exceptions rules are a great way to change behavior. Choose them quickly, follow them religiously, adapt all your other behavior around it, and then drop them.
On Tuesday and Thursdays I will send max 3 emails and none longer than 2 paragraphs. Why 3 and not 4? Doesn't matter. 3 is easier to remember. Just do it, don't break it. Reorganize everything around it: make more calls, reschedule things, whatever it takes. Is it a little bit silly and maybe even inefficient? Yes, it is, but if you have a problem with email and day after day you find yourself getting stuck in them and spending way too much time writing stuff you're not sure anyone really needs, this kind of "absurd rule" is just what you need. Do it for a while and you'll learn so much about your behavior and what drives it.
Every Monday morning, before anything else, as soon as I have a coffee in my hand, I go an talk to Michael about my latest idea. Do you really need to do it every Monday, objectively speaking? Can it be after lunch and not first thing? Sure, it could, but if it's hard for you to do it and you want to create a habit out of it, accept no nuances.
Use behavior busting rules to disrupt the things about you that you'd like to change but can't. They're the equivalent of a cold shower, of an unexpected run in the night, of an unplanned journey. Change things.
You can use it on others, but try it on yourself first.