I had similar experience with being able to get through whatever i had to do (as recently as May i managed to get through a 12 hour mediation session ) but afterwards took me 2 days at home resting. I think to some extent we learn to adapt, push through but then our body forces us to rest, rcover. Bad news from my perspective that despite lots of mestinon, prednisone and one dose of ivig i couldnt do that again.