We have been lucky to be able to spend 3-12 months at a time in various places around the world, trying our hand at living the ex-pat lifestyle.
Success at integration is very much a factor of having the attitude and aptitude to learn the language and accept the social customs of your new home. You either do this, or you spend all your time huddled in an ex-pat enclave feeling the entire weight of a foreign culture pushing in on all sides of your bubble - through the TV, the labels on the products at the store, the impatience of every person you deal with outside your enclave.
You don't have to travel far to see this in action. Just look at all the Chinese, Greek, Italian, Indian, etc. enclaves all over Toronto where these ex-pats/immigrants never learn English and never leave their community. Do you want to live like that in your new country of residence?
Suffice to say, adaption is primarily a matter of age. Once you reach a certain age, you are either unwilling or unable to change. Immigrants move to a new country for their kids. We spent over 3 months in Botswana and fell in with a bunch of ex-pats who accepted us in their circle. They spent every weekend together, the same 20-25 people - white South Africans, British, Australians, Canadians, Germans, Swiss - clinging to each other out of a familiarity with a common language and custom.
Meanwhile all their kids were hanging out with their Motswana friends from work and school, moving in and out of English and Setswana with the ease of a local.
We saw this same thing play out in almost every single country we visited. Although it was a easy and comfortable slotting in with the ex-pat communities, when we had hosts who had integrated into their country, it was a such a feeling of freedom and to an extend, relief. We stayed with a British ex-pat in Mexico City. He had lived there for over 40 years, had a Mexican wife, all his friends were Mexican. He took us around to all the local places, had favorite Mexican TV shows and music, introduced us to all the local customs, spoke fluently and with ease with everyone around him. The entire country was his to live in and explore. He wasn't confined to an ex-pat cage.
Comments on here about "banana republic", "malaria", blah blah are neither here nor there. If your mindset is rigid, you're not going to be able to live in highly-industrialized nations like Japan or Spain either.