"Human love lives by uncontrolled and uncontrollable dark desires; spiritual love lives in the clear light of service ordered by the truth. Human love produces human subjection, dependence, constraint; spiritual love creates freedom of the brethren under the Word. Human love breeds hot-house flowers; spiritual love creates the fruits that grow healthily in accord with God's good will in the rain and storm and sunshine of God's outdoors."
"Spiritual love will speak to Christ about a brother more than to a brother about Christ. It knows that the most direct way to others is always through prayer to Christ and that love of others is wholly dependent upon the truth in Christ."
"Because Christ stands between me and others, I dare not desire direct fellowship with them. As only Christ can speak to me in such a way that I may be saved, so others, too, can be saved only by Christ himself. This means that I must release the other person from every attempt of mine to regulate, coerce, and dominate him with my love. (emphasis mine) The other person needs to retain his independence of me; to be loved for what he is, as one for whom Christ became man, died, and rose again, for whom Christ bought forgiveness of sins and eternal life. Because Christ has long since acted decisively for my brother, before I could begin to act, I must leave him his freedom to be Christ's; I must meet him only as the person that he already is in Christ's eyes."
(all quotes from Life Together by Dietrich Bonhoeffer)
These words are written of the love of Christian fellowship, or philos, but it seems to me that they also can be applied very aptly to eros or romantic love. And, since the desires of eros are so much stronger and more clamorous and inherently selfish, the need to surrender them to Christ is correspondingly more vital.
But does this mean that we are to live some sort of sterile, "purely spiritual" life, without emotion or human attachment, either in fellowship or in marriage? Even if that were possible, I think not. God created all our loves, and wants us to experience and enjoy them; but in submission to His will and His unselfish (or, as Lewis would call it, "disinterested") love. It is not the affection, or friendship, or erotic desire that is the sin: it is the disordered need of the fallen self to use the other for one's own fulfillment, gratification, and reassurance. Once the will, the self, and the needy, dependent types of love have been surrendered to Him, He gives our loves back as something higher and better, in the same way that He gives back ordinary bread and wine as His transformative and cleansing body and blood.
“When He talks of their losing their selves, He means only abandoning the clamour of self-will; once they have done that, He really gives them back all their personality, and boasts (I am afraid, sincerely) that when they are wholly His they will be more themselves than ever.” -- C.S. Lewis, The Screwtape Letters