Anticipating exhaustion

Tomorrow is my first day back at college, a day of enrolment when would-be students who want our courses come along, get assessed and, with any luck get placed on a course. I'm just hoping that it isn't quite so manic as last year.
I then have a few days more off before I'm back next week on Wednesday for a couple of weeks more enrolment and then back to the bit that's why I do it - the teaching.
If I'm missing at all in the next few days it's because I'm too shattered to write anything.

Seeking a simile

I spent my Metro ride home this evening trying to think of a suitable description for how I felt.

"I feel like I've done six rounds with Mike Tyson" is rather too well-worn a cliché.
"I feel like I've been run over by a steam-roller" doesn't really capture the all over weariness.
"I feel like a house fell on me" is a dull and prosaic simile.
"I feel like a ball in the lottery machine" would be open to too many alternative interpretations.
"I feel like I was standing in the way when the buffalo started to stampede" is getting pretty close.

I never did come up with a suitable answer but there is an upside. The next time I feel like this I'll know just what to say, "I feel like I've just done a day's ESOL enrolment."