So you are comparing the existence of an emotion with the existence of a universal creator? Are you suggesting that they both reside in your head? (Which means that either or both can come and go depending on how you feel and your brain chemistry?) Now I think we're getting somewhere.
Love is a projection of what in psychological terms can be called the true self, it's the ideal balanced psyche, if you have a spiritual bent then call it the higher self Unfortunately when we unconsciously project this eternal perfect ideal onto our partner they have zero chance of living up to it seeing as they are just as flawed as everyone else So what usually follows is stress building up from our subconscious as we feel betrayed by this god/goddess not living up to our projection.. this all happens below our self conscious awareness so we cannot even take steps to deal with it rationally Hence we fall out of love