I usually go ahead and use the "Stupid." After all, in places where the KISS principle makes sense -- which, goodness knows, is not everywhere -- well...
I ARE STOOOOPID! As, indeed, are most of us.
The simple is good so I can handle things on my "stupid days."
Xenophon
P.S. My usual description of those days goes like this:
Some days I feel smarter than other days. Today is one of the other days!