Hang on in there Jules. It won't hurt to take it easy for a day or two. I felt exactly like that last night - in fact I felt fat and lethargic when I got in, the result I suspect of cramming about 20 days activity into 6 days here.
Long story short I stared at my running shoes so long the sun went down and a storm blew up. I didn't run and actually felt much better this morning after a mammoth (for this trip) seven hours in my snarf chamber. Listen to your body. Stress is a real bastard for knackering you out too - I had a stressful couple of days out here (missing trucks, pissy exhibitors) and I'm sure that contributed a lot to last nights' mini- rebellion.
I know you're in great shape. Give yourself a day off, have a few jars and get some good, deep sleep. You'll be back in the swing in no time