(4) is common among people who move internationally more than once or twice. Making friends as an adult is already difficult, and knowing that you will move on

(4) is common among people who move internationally more than once or twice. Making friends as an adult is already difficult, and knowing that you will move on after a couple of years makes it even more difficult. You have a reason to socialize with your coworkers, so they will become the center of your new social life. If you moved to a popular expat destination, you may be able to find other expats who are similarly disconnected from normal life. Beyond that, making friends requires crossing cultural barriers, which takes a lot of effort and extraversion.