Every now and then when I'm entering data, I find that my eyes have come unfocused, and I've been thinking about something (I rarely remember what) for some unknown amount of time.
I read what's on the screen, but I don't recognize it. I don't read this stuff, I just type it.
So I scroll to the bottom of the list and find that yes, two or three or five minutes ago, before I started thinking about what I'd make for dinner or the book I'm reading or the tone of that email I just received, I did enter that project.
I'm hoping it's just extreme boredom and not some slow mental decay that's causing me, more than once a day, to find myself staring at a corner of my screen, unaware of what I've just been doing or thinking.