I fall into routines pretty easily too, without even trying it. It's how I forgot to take the PSAT's when I was a sophomore in highschool.
Story:
My Honors Geometry teacher decided it would be a good idea to have the class take the PSAT's for whatever reason, so she signed us up like a week before. Anyway, everyday I'd wake up at like 6:00, shower, walk the dog, and then head to school at about 7:00 to go play chess. On the day of the PSAT, I walked into school, played chess, went to my locker, opened it and grabbed my books. I then proceeded to stare at my locker for a minute, wondering if I'd forgotten anything. With a mental, "Nope," and a resounding slam of my locker shut, I went to class...Ten minutes later I realized I'd forgotten to go to my 3rd hour classroom to take the PSAT. When I went to my 3rd hour class as normally scheduled, everyone (who was taking the PSAT) looked up at me and it was pretty embarrassing. I tried to be quiet, and I had to sit on this one stool, but it was like a fucking elephant was wreaking havoc in the classroom.
Oh well; at least I had a free hour to read Muhammad Ali's autobiography. B^)