Intimacy (and I mean emotional intimacy, not sex) is the cornerstone of a lasting relationship. Intimacy means being completely open to your partner, no walls of any sort. Intimacy means you can share everything, from the tiniest little details to the gigantic crushing disappointments that befall everyone.

Lest this point be forgotten, I shall reiterate:
INTIMACY DOES NOT MEAN SEX! Intimacy as about cuddling and sharing and smooching and nuzzling and spending time together. People who forget about that build their relationsips around sex and call it intimacy, then wonder what happened when it all falls apart. I've seen it happen to more than one friend, which is why I guess I'm such an advocate of virginity. (Beside that is the whole religion thing, but I don't want to get into that, because it will start a holy war.)