If it helps at all, I see it as a kind of waking up within the Tes universe. It is either realizing the whole thing is fictional, or realizing it is all the dream of the godhead, which in essence are about the same thing, as dreams are fictional. When you have CHIM it is pretty much assumed you have quite a good deal of power, being on a god-like level, if not a god yourself.
One of the most frequently cited achievers of CHIM is Vivec, who used it along with his Lorkhan powers to become the uber face [censored] dude he is today. He actually wrote about it, but I fear linking the page would raise more questions than it would solve.
Another person who achieved CHIM was the first Tiber Septim, better known as Talos, who changed Cyrodiil from a jungle into a forest for his people, all with his CHIM powers. He changed the terrain meshes and ground textures basically
Of course, I can't find this, so I have a very good chance of being wrong, as I frequently am. Just waiting for someone to prove it though
Interestingly enough, no one has bothered to make a UESP wiki page on the subject, a matter I find both hilarious and a little frustrating, as that's where I go for basic summaries when I need some non-specific information.
I know I'm wrong on this, but there are very few people are right when it comes to CHIM. Closed fridges don't count, or whatever crazy metaphor you wacky kids are using nowadays.
EDIT: Ah, and if you were curious what they meant about the difficulty achieving CHIM, it is basically realizing you are a part of everything, all of the world basically the godhead's dream, and still being able to retain your individaulity, most commonly expressed when people reatin the ability to say "I". I don't know what happens if they lose their individuality, but I assume it 'tis bad. Once again, I know I'm wrong, but that's just my hazy misguided interpretation based on what I've read here.
:whisper: These folks aren't the most helpful anyway :whisper:
Kidding, I don't know where I'd be without the wonderfully helpful lore forum and its inhabitants
Cheers!