It doesn't matter how smart you are, we all have our "stupid" moments from time to time.
In some cases, someone widely known for being smart makes the most ridiculous gaffes, because they're so uniformly focused on what's floating through their mind, they forget how to function like a person.
Remembering that even people lauded as geniuses make ridiculous snafus can be helpful when you're down on yourself.
When I was in my final year of physics at university, we had a professor who would get very irritated at the pull string for the projection screen, as it would dangle down in front of the whiteboard.
Every morning, he would spend a good couple minutes attempting to throw the weight on the end over the light fixture above the whiteboard, taking anywhere from 5 to 30 tries each time.
All the students would give tips and encouragement, and this became a kind of inside joke for the class of how long it would take every morning. Months go by, and one day near the end of the quarter, we end up with a substitute.