Love, like any other emotion, is "just" an experience. It may or may not lead you to action. People are complex things and not all are capable of responding to their emotion's motivations.
Love, at it's heart, is opening - a "yes", an acceptance. Only when judgment or attachment enter can love morph into "a kind of love", or something less than the universal "yes".
We do not grieve because we loved those lost to death, we grieve because we are attached to them (and rightly so). We cry because of our sense of loss, for ourselves and for them, for what might have been yet in the future and for their absense in the present. Because we loved them, we miss them now - but it is not the love that causes us pain. It is the loss that causes us pain.
When we see someone give, we don't know what their motivation is. It may be compassion. It may be empathy for someone's plight. It may be guilt. They may be coerced by another.
In some sense, love is not a reason to do anything. "If you loved me, you would __________". Love is not something you can hold hostage, nor is it something that would motivate you to action in that kind of scenario.
In some sense, love is a realization that you are part of something larger than your self.
Love is also a word, like God, that is often spoken with an implied understanding, only to find that no one is speaking about the same thing.