I can't do the Timeless Isle anymore. Not on my main, not on any of my alts, not even the ones that could use the gear. I simply can't do it. I mean that - even attempting to go there makes me decide to do something else. Anything else. I'd rather spend four hours farming away on the Isle of Giants gathering dinosaur bones (or letting my wife collect all of them) than go to the Timeless Isle.
There are other things I can't bring myself to do in game. I can't run Sunken Temple. Every time I go in there it's like my brain forces me to come up with a reason to leave. And I'm beyond terrible at playing a paladin - every time I try I end up getting myself stuck at some random level, and often, I end up deleting the character. I recently started playing a paladin I'd left at level 50 since vanilla - he's since been deleted. I have friends who simply cannot play Horde, or Alliance.
So, let's ask the question - what can't you make yourself do anymore? What couldn't you ever do?