There is a difference between being enthralled/infatuated by someone, and being in love with someone. Enthrallment or infatuation is when you are consumed with your desire for someone else. Love, on the other hand, is the giving of oneself to another. It is caring for their needs as you would your own. It is doing all you can to make them a better person. In short, infatuation is self-consuming, while love is self-giving.
I tend to think that we have so confused the two in our culture that only a minority of couples ever experience true love. Instead, they experience intense periods of infatuation in the beginning of their relationship, and that gives their relationship the gas it needs to continue for a considerable distance. But like a car that only gets filled with gas in the beginning of a long trip, the relationship does not reach its intended destination of “til death do us part.” Only true love (or pure will and commitment) can fuel a relationship so that it can endure the many hardships of life.