How do you feel on those days? Miserable? Crappy? Fed up? Cheesed off? Really? Why would anyone want to equate feeling crabby with cheese? Doesn't everyone feel happier when they eat cheese?
From what I've been able to glean from various internets, including Merriam Webster and "World Wide Words", the phrase is British in origin, and strangely Merriam Webster lists its year of origin as 1942. And darn those Brits, but apparently in olden times, they didn't like their cheese stinky (though they do make amazing Cheddar and other tasty cheese). Sadly, the phrase "cheesed off" refers to the delightful "stinky" smell of cheese. I have this vision of a miserable Brit having a bad experience with a washed rind cheese that had just been patiently waiting for someone to come and love it, sending its fumes off into the world looking for a friend, only to run across this crabby patty, who wrinkles up his nose, and the rest of his day is ruined. To his mind, that complex, charming cheese was "off," and from that day on, whenever he was having a really miserable day, with his quirky British sarcasm firmly in place, he would tell people he was cheesed off. Somehow, it caught on.
Anyway, that's just my version of events. Please feel free to share your own version of events!
Sleep on it. Wake up happy, and try always to eat cheese not get cheesed off!