Shack tidy-up: exhausted!

This afternoon I attempted to do, what in the past, would have been totally trivial: tidy up my shack a bit. After trying to sort just a couple of boxes I was totally exhausted. This is still an after-effect of my cerebellum brain bleed in September 2013.  Although, on the whole, I get less tired than I did, I still find that almost any burst of physical or mental activity leaves me exhausted.  I just have to relax, then I feel better. About 10-15 minutes and I am "done in". Oddly just walking or driving don't have the same effect. I have been able to walk about a mile OK for a year or more.