I agree with the not overthinking it part. Most flats on the course are pinch flats. Do your best not to slam into rocks and holes and you'll be OK. If you get into a situation where you can't help slamming into stuff, c'est la vie.
Last year a friend was in a break of 3 at mile 50 with 2 minutes on the field and flatted. He was carrying a tube. He changed it fast enough to catch the end of the peloton as they went by.