Have you ever tried on a pair of green shoes? You loved them but, really, when are you gonna wear bright green shoes? Still, you couldn't stop thinking about them for the next 10 days straight. You went back to the store, bought the shoes and never looked back. Gradually, your wardrobe changed so that those green shoes looked great with a lot of what you wore.
Or maybe that's how you knew you were in love with your lover. You met that person and they weren't the best looking, smartest, wittiest, the whatever-est person you had ever met but nonetheless, you could not stop thinking about them. They didn't fit your checklist of what you'd look for in a partner. No matter, you wanted them in your life and, pretty soon, your life had changed because they were in it making you a better person.