This article was so good, I had to include the whole thing, from Holy Spirit Interactive
On True Love by Alice von Hildebrand
Reason speaks in words alone, but love has a song. —Joseph de Maistre
We live in an age of confusion. It might even be said that we major not only in intellectual confusions but in affective confusions as well. Many do not know how to gauge their emotions; they cannot distinguish between valid and invalid feelings. They do not know for certain whether they are truly in love or whether they are animated by wishful thinking and believe themselves in love because they crave the excitement that love gives. They confuse "loving" with having a crush, or "discerning" forever without coming to a decision.
Far from claiming that I can answer this question, all I aim to do is offer some "signposts" that might be helpful when people ask the question: Am I or am I not in love?
Great experiences usually come as a surprise—incredible gifts that are in no way the fruit of wile or planning. They overwhelm us, and our first response is: "I am not worthy of such a gift. He (or she) is so much better than myself." Our hearts are overcome with gratitude, a gratitude that makes us humble. We feel unworthy of such a gift, which seems to awaken us from a deep sleep. No doubt, the person in love "truly starts living." The person who has never loved lives in a state of somnambulism and moves about as an automaton fulfilling his daily duties with dullness of heart—a heart that does not seem to beat.
When in love, we experience a deep, profound joy—a joy that is both ardent and calm, like a burning bush; but this ardor is not destructive, and is marked by deep recollection. It springs from the very center of our being. How different from the loud excitement of those who experience violent emotions that do not come from their depths and, like a straw fire, shine brightly for a short while but are soon extinguished.
The heart is not only on fire, but this fire has a melting effect. We feel as if a goodness that does not come from within has taken hold of us. Dietrich von Hildebrand speaks of "fluid goodness" of a loving heart.
True love makes the lover more beautiful; he irradiates joy. If this is not the case, we can raise doubts as to whether he is truly in love. One says in French: "Un saint triste est un triste saint"—a sad saint is a pitiful saint. Similarly, a sad "lover" should question whether he truly loves. Small, modest duties are done joyfully, because either they are done "with him" or "with her," or because they become acts of loving service.
True love makes one humble. All of a sudden our weakness, misery, and imperfection flash up before our minds, but with no depressing effect. We see our mistakes with the wish to unveil them to the loved one, and this unveiling is coupled with the wish to beg for his or her help in order to overcome them. We wish to unveil ourselves spiritually in a chaste way, to be truly known by the person we love; we fear to cheat our beloved into believing that we are better than we truly are. We feel that the loved one is entitled to know both our "valid name" and its caricature.
Love is also linked to a holy realism. The beauty of the loved one appears in front of us, but with no illusion; his beauty is not a fruit of wishful thinking, but a real vision—as on Mount Tabor—that the lover will have to remain faithful to, to hold on to when the vision is inevitably dimmed by the dullness of everyday duties.
The lover will always be willing to give the loved one what Dietrich von Hildebrand calls "the credit of love"—that is, when the loved one acts in a way that we do not understand or is a disappointment to us, instead of condemning him, the lover will trust that, human life being as complex as it is, his actions may be justified, even though at first glance they strike us as regrettable. The true lover eagerly looks for "excuses" when the conduct of the one he loves is a disappointment. He carefully refrains from being overconfident in blaming the other’s conduct, baffling as it might be at first sight. He rejoices upon discovering that he was mistaken.
How sad it is in Shakespeare’s play Cymbeline when Posthumus, being informed by the scoundrel Iachimo that his wife, Imogene, had betrayed him, believes the slanderer, even though he had ample previous evidence that she loved him and was pure. The play has a happy ending, but it sketches powerfully the bitterness, rage, and despair of someone who is convinced that the one he loved, the one whose image was the source of his joy, has betrayed him.
We can say that we truly love when a loved one’s impatience, ingratitude, or "rudeness" (in other words, when his true beauty is veiled) cause us greater grief because he is staining his beautiful garment and presenting us with a caricature of his true face, rather than because he has wounded us. Most of all, the true lover is grieved because the loved one has offended God. On the order of importance, the offense against God is the primary source of sorrow; the harm that he does to his own beloved soul is second; last—even though deeply painful—is the wound he inflicts upon the one who loves him so deeply.
The true lover is more concerned about the interests of his loved one—whatever truly benefits his beloved’s soul—than about his own. Hence the readiness to make sacrifices for him in the very many little things of daily life in which people’s tastes differ: a very warm room or a cool one; eating at home or in a restaurant; going to a soccer game or staying home; watching a television program when one’s spouse wishes to watch another one, and so on. Yielding should be limited to cases of subjective preferences, of course, and should never extend to principles. Still, we all know spouses often ill-treated by their husbands (or wives) who are so concerned about the eternal welfare of the loved one that they accept all these sufferings, offering them up for his or her sake.
A great sign of true love is the loving patience that one has toward the weaknesses of the beloved. It can be his idiosyncrasies, his temperament, his mannerisms (we all have them); it can be his physical frailties, his psychological oddities, his intellectual inability to follow a straight line of reasoning; his disorder, or his fanaticism for order. If a monk is constantly given occasions to "die to his own will" (as St. Benedict says), the same is true of marriages. John Henry Cardinal Newman writes that even in the deepest human relationships, when love is authentic, life in common will give one plenty of opportunities to prove one’s love by sacrificing one’s preferences.
Mannerisms, idiosyncrasies, moods; physical, psychological, and intellectual weaknesses are either interpreted as positively as possible or are borne with patience. Benedict writes about monks striving for holiness who nevertheless almost inevitably cause irritation for those living close to them. "Let them bear with the greatest patience one another’s infirmities, whether of body or character" (Holy Rule, chapter 72).
The History of a Soul, from this point of view, is also a spiritual treasure. St. Thérèse of Lisieux clearly suffered much from the lack of education and manners in some of the other nuns. She learned the holy art of using every single irritation for God’s glory, including the nerve-racking noise that a sister made in the stall next to hers, which prevented her from praying and being recollected. Still, Thérèse emerged victorious through love.
Surprisingly, this can also bring happiness to the best of marriages, even though the being we love has wounded our hearts. A true lover whose love is baptized will use these insignificant sacrifices as they did in the Middle Ages, when artists used some bits of wool to make superb tapestries.
The true lover always has the word "thank you" on his tongue. It is also easy for him to say "forgive me," for in the best relationship, one inevitably falls into mistakes. If someone imagines that he can find himself in a situation in which he will never make a mistake, that person should not get married, or have children, or enter a convent. The holy art of living is to know that we will make mistakes, to recognize them, to repent, and, with God’s grace, to have the readiness to change.
Simultaneously, it is important that both lovers recognize their mistakes. We all know cases in which one of the lovers is always critical of the other and easily forgets that "the readiness to change" should be reciprocal, and that he too is affected by original sin.
Another characteristic of true love is that the loved one is "superactually" always with us; he is there, even when we are busy or absorbed by some duty. He creates the framework of our thoughts (after God). Just as faith in God and love of God should always be the background of all our thoughts and actions, the loved one is always with us; that is, everything that occurs is never unrelated to our love.
The lover feels a holy urge to say "thank you" and "forgive me." It flows from his heart without effort. The true lover experiences the deep truth of the words in the Canticle of Canticles: "If a man were to give the whole substance of his house for love, he would despise it as nothing."