I think this checks out for most people.
Being "in love" refers to the heady feeling of infatuation characteristic of the initial stages of a romance. And while it's nice and all, I've never found it to be sustainable — nor would I want it to be. As with any sort of intoxication, it's a very subjective experience and has more to do with the way you
feel rather than a realistic dispassionate appraisal of the situation.
How you feel after you've fallen "out" of love is more significant, if not as exciting. Do you spurn the feelings the other person once aroused and resent the time and energy you've invested? Or, feeling valued and accepted, do you accept and value the other person as they are, for what they are, and not as the embodiment of some personal conceit? Being strongly "in love" may be transient, but it has its uses. Especially when, years later, you recognize the characteristics in the other person that led you to fall "in love" with him in the first place.