I have come to believe that what is called "in love:" the ecstatic "high" from the anticipation of being with someone new and exciting, the sexual chemistry, and the verbal proclamations of love, has to do with animal chemistry and the species' drive to procreate! I know this sounds cynical.
True romantic love can and does survive beyond this initial "high," I suppose. I've just never been fortunate enough to experience it! Something wrong with me, I guess!
Patty