As a person without ADHD, I handle my reaction to it by apologizing for misunderstanding, and then moving on. Even if the misunderstanding doesn’t seem to be my “fault”, taking the blame is a small price to pay in order to keep things relaxed.

I know it’s got to be incredibly embarrassing and frustrating, but I also know that I can’t really understand what it’s like to have ADHD. I just try to make it clear that I’m not upset (while at the same time not dwelling on it) and I try to make the other person as comfortable as possible. These things happen.