Admittedly, I don't have a lot of personal experience with healthy stupidity.
I'm a fairly bright guy, by human standards, and most of my experience with genuine stupidity stems from a period of my life where I was recovering from stroke-induced brain damage, which is at least arguably a form of unhealthiness.
That said, I think everyone is familiar with the effects of fatigue on cognition. It's harder to hold onto a train of thought, it's harder to account for emotional bias, it's harder to keep things in memory. When I get tired, I get stupid. It's a kind of mental fog.
When I was recovering, I felt like that all the time.
Partly, of course, that's because I was genuinely tired a lot of the time, in large part because my blood pressure was being artificially lowered and I was greying out a lot.
But even when I wasn't tired -- during those brief blessed windows after waking up and before I started physical therapy, for example -- there was still that characteristic mental fog, all the time.
That's what I was thinking about, when I wrote it.
That said, I have no idea whether healthy stupidity feels at all like that.
Okay. Considering that you were genuinely tired during the time period about which this observation was made (and that your tiredness probably facilitated stupidity, rather than the other way around), this does seem like an indicator of tiredness rather than stupidity, so I'm going to leave it out for now. Thanks for the explanation.
In Anna’s recent post, she talked about training your mind to notice when it wasn’t curious about something and scream “Error! Look for a different way to do this” in such cases. Johnicholas and TheOtherDave's list of what stupidity feels like also looks useful for this purpose. I'm creating this post to make a more comprehensive list of feelings which indicate that people should reanalyze different possible paths to make sure that the one which they're taking is the most effective one to their objective.
Please suggest additions to the list in your comments -- I'll move them up here (along with links to further explanation, if given.) Keep in mind that your description of the feeling should be as illustrative as possible. For example, "feeling stupid" is unhelpful, while "you feel like you've taken a wrong turn into a never-ending tunnel" is better. Of course, metaphors which are immediately understood by some people may not be so easily understood by others, so try to give a more detailed description of the feeling if other people express that you're probably saying more than they're hearing.
List: "Error! Look for a different way to do this" if you feel like: