I've played many times when I was absolutely beat. I hated it. I felt like I wasn't really into it and just going through the motions. I honestly felt like a zombie. That feeling usually lasts for the first set. After that, I generally 'come to life' either from feeding off the audience or by "forcing" myself to wake up some. I'll go out to the truck and crank up some KISS, Ted Nugent, Sabbath, G 'n R, or anything that pumps me up some.
We play from 8-12 every Sat. night. I honestly wish it was from 8-1 or even 2.
After saying all that though, I have been known to over do it in the past and would never go through that again. In the 80's, I was playing 5-7 nights a week and working in a factory (we started at 6 am). That was too much, and it really took it's toll on me. It, combined with the "live fast" lifestyle I was living, almost killed me. I was in my early 20's though and didn't think about it.....until one night I met this girl at a club.
Skipping the details.......the next morning we're talking and she admits that she'd never been "with an older man before". Older man?? I asked her how old she thought I was and she replied "about 44."

Needless to say I told her my age.
I wonder what ever happened to her............
Joel