of course you could say "Monday Sickness" any day of the week.
Chris: nah, its a Monday. i think im going fake sick
John: ah, going with Monday sickness, eh?
Common symptoms include:
Lowered brain functions,
and an overall feeling of human (Or otherwise) excrement.
*Jimmy sees it's Monday*
*Jimmy goes back to sleep*
1: "Dude, I got a 57% on that test last Monday..."
2: "That's Monday Sickness for you..."