Years ago I knew someone who had everyone "labeled." She had her "camping friends" and "symphony friends" and so on for every activity she was involved in. She even introduced me as her "movie night" friend to someone once. The thing was, when it came time to mix friends, she wouldn't do it. We had a mutual friend (who was in one of her other "groups") and I suggested that this person might enjoy seeing a movie with us, and she nixed it because that person was in her other group. Like this person couldn't go to a movie with her because she was in her dinner group! I thought this was silly, but she had gotten so used to doing certain things with people that there was no room in her mind for anything else.
I think "friend groups," which my pal had, can be a very good thing. But like anything, if you take it to the extreme, it can dominate your relationships. My friend basically didn't make new friendships because she didn't know where she would "put" anyone new in her life. I think we all get into ruts and fall into a rhythm when things are going well, but to limit who you do things with? It can make you a very dull person.
If the whole of your relationships consist of friend groups, maybe it's time to shake things up a bit. Not sure of what friend groups really are? Here's a definition, along with some advice on how to make them work for you.