I'dve thought this was just a cute Annie-ism, but the concept of soul-mates is essentially just a more romantic less platonic version of this idea.

I dunno, perhaps I'm projecting, but I don't think most people actually believe in soul-mates, its just that they find it a cute concept and haven't really thought the implications of it trough.

I think most people would admit if pressed that there isn't really one perfect match for you, there are people you'd fit well with, people you'd fit not so well with, and people you think you'd fit well with until it all blows up in your face. Love tends to explode a lot.