I choose my friends because we have something in common. They mesh with my personality, likes, interests, hobbies, etc. I choose my significant other because we have something in common. She meshes with my personality, likes, interests, hobbies, etc. While I don't necessarily expect my s/o and my friends to get along on everything, they should have at least something in common they can connect on. If not, then either I'm not a good match for my friends, my s/o, or both.