Limerence is an involuntary state of mind which results from a romantic attraction to another person combined with an overwhelming, obsessive need to have one’s feelings reciprocated. Psychologist Dorothy Tennov  coined the term “limerence” in her 1979 book Love and Limerence: The Experience of Being in Love  to describe the concept that had grown out of her work in the mid-1960s, when she interviewed over 500 people on the topic of love.
Being “in love”—limerence—is involuntary; you have no conscious control over the creeping obsession and the hormonal-biochemical imperative to Pay Attention to this Fascinating New Creature in your world. One common explanation for limerence is that it serves the evolutionary purpose by irrationally binding couples long enough to rear children. Some recent reading suggests a higher-level game-theoretic signalling purpose: to demonstrate that one’s commitment to the other is irrational and therefore unlikely to be broken by the attraction of a more suitable and advantageous partner. Someone considering a partner can be convinced to commit more easily when evidence shows the partner will not break the commitment just because a better opportunity comes along. The persuasive power of a display of unconditional and irrational love is enormous.
Culturally, limerence is either seen as the desirable state of hyperexcitement all romances should begin with, or the tragic downfall of clueless losers who throw themselves at people they barely know because of some delusional intuition that they must be soulmates. Both of these views are oversimplified—many or even most good long-term relationships start off with a long, slow period of getting-to-know-you, gradually easing into partnership. The limerence that may be present in one (and occasionally both!) prospective partners can help get over the initial hurdle of superficial difficulties in getting them together. Being “in love” is not a necessary or sufficient condition for partnering with someone, but neither does it hurt.
But our culture glorifies drama and passion. Novels, opera, movies all tell us sexual attraction plus passion equals Really Living. Dr. Lewis has some thoughtful comments:
Our society goes the craziness of in love one better by insisting on the supremacy of delectable but ephemeral madness. Cultural messages inform the populace that if they aren’t perpetually electric they are missing out on the pinnacle of relatedness. Every pop-cultural medium portrays the height of adult intimacy as the moment when two attractive people who don’t know a thing about each other tumble into bed and have passionate sex. All the waking moments of our love lives should tend, we are told, toward that throbbing, amorous apotheosis. But in love merely brings the players together, and the end of that prelude is as inevitable as it is desirable. True relatedness has a chance to blossom only with the waning of its intoxicating predecessor.
Loving is limbically distinct from in love. Loving is mutuality; loving is synchronous attunement and modulation. As such, adult love depends critically upon knowing the other. In love demands only the brief acquaintance necessary to establish an emotional genre but does not demand that the book of the beloved’s soul be perused from preface to epilogue. Loving derives from intimacy, the prolonged and detailed surveillance of a foreign soul. 
The rush of initial limerence is so powerful it is analogous to a psychoactive drug—indeed, some of the same neurotransmitter receptors may be involved. And by analogy, we have Roxy Music’s “Love is the Drug.” A self-help book, Peele and Brodsky’s Love and Addiction, covers the topic of people addicted to the rush and unable to stop craving it. Stalkers are people who have fallen into a pathologically deep limerent hole, unable to overcome the delusion that they have a special relationship with the stalked.
But long-term relationships are built on a much deeper jointly-built understanding, and a more real limbic connection between partners. This requires regular physical contact, a long history of supportive message exchange, and a deep sense of trust and knowledge of the other:
Because loving is reciprocal physiologic influence, it entails a deeper and more literal connection than most realize. Limbic regulation affords lovers the ability to modulate each other’s emotions, neurophysiology, hormonal status, immune function, sleep rhythms, and stability. If one leaves on a trip, the other may suffer insomnia, a delayed menstrual cycle, a cold that would have been fought off in the fortified state of togetherness. The neurally ingrained Attractors of one lover warp the emotional virtuality of the other, shifting emotional perceptions— what he feels, sees, knows. When somebody loses his partner and says a part of him is gone, he is more right than he thinks. A portion of his neural activity depends on the presence of that other living brain. Without it, the electric interplay that makes up him has changed. Lovers hold keys to each other’s identities, and they write neurostructural alterations into each other’s networks. Their limbic tie allows each to influence who the other is and becomes.
Mutuality has tumbled into undeserved obscurity by the primacy our society places on the art of the deal. The prevailing myth reaching most contemporary ears is this: relationships are 50-50. When one person does a nice thing for the other, he is entitled to an equally pleasing benefit—the sooner the better, under the terms of this erroneous dictum. The physiology of love is no barter. Love is simultaneous mutual regulation, wherein each person meets the needs of the other, because neither can provide for his own. Such a relationship is not 50-50—it’s 100-100. Each takes perpetual care of the other, and, within concurrent reciprocity, both thrive. For those who attain it, the benefits of deep attachment are powerful—regulated people feel whole, centered, alive. With their physiology stabilized from the proper source, they are resilient to the stresses of daily life, or even to those of extraordinary circumstance.
Being “in love” is the Fool’s Gold of attachment: non-nourishing, short-lived, and more a hindrance to long-term achievement than a help.
 Dorothy Tennov in Wikipedia
 Tennov, Dorothy (1999). Love and Limerence: The Experience of Being in Love. Scarborough House. ISBN 978-0-8128-6286-7.
 A fascinating operetta by Stephen Sondheim about obsessive limerence and its persuasive power : Lapine, James. Stephen Sondheim’s Passion. Image Entertainment, 2003.
 Lewis, p 206
 Roxy Music’s Love Is The Drug:
 Peele, Stanton, and Archie Brodsky. Love and Addiction. New York: Penguin Group, 1991.
 Lewis, p 207
More on Divorce, Marriage, and Mateseeking
Marriages Happening Late, Are Good for You
Monogamy and Relationship Failure; “Love Illuminated”
More reasons to find a good partner: lower heart disease!
“Princeton Mom” Susan Patton: “Marry Smart” not so smart
“All the Taken Men are Best” – why women poach married men….
“Marriage Rate Lowest in a Century”
Making Divorce Hard to Strengthen Marriages?
Student Loan Debt: Problems in Divorce
“The Upside of ‘Marrying Down’”
The High Cost of Divorce
Separate Beds Save Marriages?
Marital Discord Linked to Depression
Marriage Contracts: Give People More Legal Options
Older Couples Avoiding Marriage For Financial Reasons
Divorced Men 8 Times as Likely to Commit Suicide as Divorced Women
Vox Charts Millennial Marriage Depression
What’s the Matter with Marriage?
Life Is Unfair! The Great Chain of Dysfunction Ends With You.
Leftover Women: The Chinese Scene
Constant Arguing Can Be Deadly…
“If a fraught relationship significantly shortens your life, are you better off alone?
“Divorce in America: Who Really Wants Out and Why”
View Marriage as a Private Contract?
“It’s up there with ‘Men Are From Mars’ and ‘The Road Less Travelled’”
Free Love, eHarmony, Matchmaking Pseudoscience
Love Songs of the Secure Attachment Type
“The New ‘I Do’”
Unrealistic Expectations: Liberal Arts Woman and Amazon Men
Mark Manson’s “Six Healthy Relationship Habits”
“The Science of Happily Ever After” – Couples Communications
Free Dating Sites: Which Have Attachment Type Screening?
Dating Pool Danger: Harder to Find Good Partners After 30
Mate-Seeking: The Science of Finding Your Best Partner
Perfect Soulmates or Fellow Travelers: Being Happy Depends on Perspective
No Marriage, Please: Cohabiting Taking Over
“Marriage Markets” – Marriage Beyond Our Means?
Rules for Relationships: Realism and Empathy
Limerence vs. Love
The “Fairy Tale” Myth: Both False and Destructive
When to Break Up or Divorce? The Economic View
“Why Are Great Husbands Being Abandoned?”
Divorce and Alimony: State-By-State Reform, Massachusetts Edition
“Sliding” Into Marriage, Small Weddings Associated with Poor Outcomes
Subconscious Positivity Predicts Marriage Success…
Why We Are Attracted to Bad Partners (Who Resemble a Parent)