Recalibration Still Underway

No matter where I travel, with the exception of Phoenix, the return to Tucson always proves harder than I'd imagined. I know I'm not the only one to have this problem either, though it may be worse in my case. Right now I'm trying to figure out why I'm so drop-dead exhausted since getting back Thursday despite having no obvious malady. Also, my knees are absolutely killing me, but I haven't exerted myself that much in that time. The mysteries of the desert are many.