My 6th grade teacher told me of this quote and I'll never forget it "Be slow in chosing friends, and slower in losing them". I tweaked it a little bit, but it means the same thing.
I chose my friends carefully but I'm also careful about losing them. I wasn't always this way. I burned a lot of bridges in my past. You may find you have nothing in common with your friends right now, but you may grow to be close again.
I am facing a similar situation. A friend I know is into weird self-help books and is constantly attending self-help seminars and classes. It was interesting at first, but I grow tired of hearing about them. I have decided to create some distance but still keep her as a friend. She's a good person deep down and I don't want to lose her. My hope is that in the future, we'll have more in common like we used to. Or I can learn another way to relate to her.
I am also trying to meet people who share my interests though. You have to have a balance.