Believe it or not, having a social life is an integral part of graduate school. When I first started graduate school, most of my friends were people that were in my cohort. However, as people have started finishing, moved to other places while still in the program, or have had a variety of other life transitions, meeting people outside of my program has become more important, because the majority of friends from my program are no longer in Ann Arbor.
This isn’t easy, though. Having a social life isn’t something that is stressed in graduate school, but it should be. It can be cloying, at times, to only know, talk to, and hang out with people that are in your same graduate program. Sometimes you need an escape, and that escape comes in the form of other people.