I think we ended up together because we talked so much when we first knew each other, and we found that we were very similar people in our basic personalities, and in our life experiences. It took exactly one month of talking for hours every day for me to go from "I'm not over my last boyfriend and I'm celibate by choice" to "hey let me show you this private spot on the beach I know of." You can fill in the rest.
There were a lot of things I found out about him when we were talking that I took as positive signs, particularly that he is an animal lover and he admitted to having some of the same social struggles as me. I made note of these things and liked that he was sensitive to the same nuances as I am, plus he gets my sense of humor and stream-of-consciousness ramblings. It helped tremendously that he is quite intelligent. Once all that was established it was good that he is of the physical type that I strongly prefer (since I do seem to have a "type," which is something I didn't figure out until I was in my mid-20s) so it was easy for me to become physically attracted to him and notice all the little things that make him attractive and special. Then, after we started sleeping together, the chemistry
really began to happen so we kept doing it. Over five years later the chemistry is still there, and I'm still not bored.