|The River Raisin in the moonlight|
One excellent resource to understand agape love is this little essay by Dallas Willard - Getting Love Right - for just $1.
Willard says that agape love is not a desire, not a feeling, and not an action. Agape love is a source of action, but "is a condition out of which actions of a certain type emerge."
Love, as Paul and the New Testament presents it, "is an overall condition of the embodied, social self poised to promote the goods of human life that are within its range of influence. It is, then, a disposition or character (a second-level potentiality or potency, in Aristotelian terminology): a readiness to act in a certain way under certain conditions." (Kindle Locations 112-115)
When someone says "I just can't love so and so" and gives up on love they are going about this the wrong way. Willard says "they should not try to love that person but try to become the kind of person who would love them." That's the key - right there. "Our aim under love is not to be loving to this or that person, or in this or that kind of situation, but to be a person possessed by love as an overall character of life, whatever is or is not going on." (Kindle Locations 137-138)
A lover loves.