"Love is making a choice every single day, to either love or not love. That’s it. It’s that simple."
http://www.mindbodygreen.com/0-5379/How-Do-You-Know-When-You-Love-Someone.html This article articulates my thoughts on the matter so beautifully. But I don't quite agree that the choice to love is not just a feeling but an action- at least not in the case of a relationship between a man and a woman. Sometimes, that choice to love that someone has been made by a greater power so that we can't quite pull ourselves away from that choice and choose the alternative. Sometimes, if we're lucky enough, we meet that one person that's our other half- our soul mate- and the choice is made up for us subconsciously from the beginning. Sometimes, because we've loved for so long, we've sunk deep into the abyss and all that remains for us is to continue loving that person. Sometimes, we may not love the person the way that we were meant to, or intended to, but we love them anyway because of the obligations and responsibilities that have been imposed upon us (case in point; arranged marriages).
Sometimes though, we fall in love with that one person that's made for us, but we can't be together with that person in this lifetime because of the many factors in our lives. We can't stop loving them simply because that choice is too painful entirely, and so we continue loving them even knowing that they would not be ours. This is the kind of love that will cause us to suffer our whole lives because it's so consuming, but it's also the kind of love that has the power to last and never die.