Why you can't apply word to things like "I will be size 5"

It's because giving you word can only work where it is applicable.

And it DOESN'T APPLY to UNKNOWNS.  Any time the question "How do I apply word here?", determining if it's 100% unreasonable or not is impossible... even if it's 99.9% vs. 0.1%, there's a grey zone, and it begs the question.

100% Unreasonable Word only applies to areas that are 100% Clear on What To Do.
(100% unreasonable where 100% rational)

Saying "I give my word to always go for size 5" doesn't work because you'll be making calls and an urgent email will come up, and then you won't know how to apply it, how to measure, etc... and you'll need to figure it all out... and then it's unclear if you're unreasonably following a choice or not.

Word has to be clear.  It works on the morning ritual because it is incredibly clear: "Regardless of sleep, dream states, etc etc... at 430 you will pop out of bed and go directly to cleaning mouth guard, drinking water, throwing on music and doing exercises."

The more clearly defined, the better.  If it's unclear HOW TO BE 100% UNREASONABLE, then the concept doesn't apply.