China ends up getting to even the most patient and open minded people with enough time.
The place is depressing, living in a grayish concrete hell and being singled out on a normal basis.
Even when you speak the language, you are still a transient outsider to most of the locals.
The money centered society where anything that's not profitable is being crushed.
The impossibility to project yourself into the future, to make plans, because of the visa system.
I've seen naturally optimistic fellas turning into depressed nihilists after a few years in China.