US Champs - how can I be so bad?

I travelled over 10 hours to Virginia to compete in the US Orienteering Champs at the weekend, and did really badly.
I just couldn't seem to navigate correctly on the terrain, contour details seemed vague and it was nasty green everywhere. I retired for the first time ever on Saturday after being out for 2.5hrs and only completing half the course, it was still over 5km back to assembly from where I gave up. Sunday was better (map below) and I finished 11.2 km in 1:54 hrs, mainly down to one stupid mistake (> 10 mins) part way round and then getting too tired at the end.

maps.google.com

Prince William Forest Park, Quantico Orienteering

I enjoyed Sunday's course much more, despite overlap with the previous day's terrain. Either I'd learned something from Saturday or I preferred the planning style but I was able to plan a proper route on it (seemed more options for using the larger re-entrants rather than having to cross lots of vague ones) for most controls.

US Champs website