Why do I like someone so fast and so passionately?

I am picky in that I can’t be sexually attracted to and like just anyone. However when I meet someone who is both physically and intellectually appealing to me, which is quite rare, I like them instantly and passionately. It feels unhealthy as I always end up getting heart broken. Why is it that I ‘fall for’ or start liking these guys so fast? Could be after one conversation or one date… I just am down to be with them and work around our differences.

This is now happening with someone who only seeks casual sex, has had many sexual partners in the past and doesn’t like relationships. I don’t understand how I can feel so passionately about someone like this so quickly as it won’t work, he doesn’t care about it…

Why is this? Am I needy, or weak? I am completely fine alone by the way (doing things alone, being single etc.) but I am also a hopeless romantic.