I had to do the reverse for a job - SO stayed in US, I went to Asia.
One of the most painful times of my adulthood... that was the hardest part about it - I missed him ALL the time, to tears often. We had frequent misunderstandings due to asynchronous communication, a couple of which almost resulted in breakup.
We held on for dear life and basically decided from the beginning to stick through it no matter what happens, and wait to see each other and be with each other again on the other side to make any decisions about our future.
He ended up proposing to me about 6 months before I was due home to the U.S. and I said yes.
We're getting married in a couple months