What kinds of things do you mean by "acts of stupidity?"
I just don't really know what to say. I can't say that something one person is doing is stupid because I know I'm going to turn around and immediately do something stupid, myself. And that would be embarrassing.
So, I guess I would try to remind myself that, as the OP mentioned, the person doing the thing I think is stupid doesn't realize they're being stupid, and they aren't doing it specifically to annoy me, so I try not to be so hard on them. I help them to see maybe a better way of doing what they're doing, if I can and I think it will help, and otherwise, I mind my own business.