Remember the first time you fell in love with someone who didn’t want to be with you? The total high when he looked your way and the gut punch of his cold shoulder? The agony of unrequited love gets Baz Luhrmann’s extravagant treatment in a new movie version of F. Scott Fitzgerald’s “The Great Gatsby,” coming to theaters May 10.MORE: How to Be Lucky in LoveIn the story, Gatsby and Daisy, played by Leonardo DiCaprio and Carey Mulligan, are teenage sweethearts separated by the war. Daisy has since married a rich, powerful man, Tom Buchanan, and Gatsby is doing everything he can to get her back. He becomes a self-made millionaire, buys a house across the water from hers and throws lavish parties hoping to see her at one of them. He finally does rekindle the fire, only to have his heart broken again when she won’t leave her husband.Gatsby is disturbingly obsessive, but his response to lost love is a heightened version of what we all go through. It’s a natural, chemical reaction.When we are rejected or ignored by someone we love, our brains shift into autopilot. Our reptilian brain turns on—the part of the brain that’s pure instinct, beneath logic or emotion.In the brain of a scorned lover, three major regions light up. First, the reward system. It makes you crave and desire the person and focuses all of your attention on getting them. Second, an area of the brain that measures gains and losses makes you much more willing to take risks. And third, a region linked to emotional attachment makes separation painful.MORE: The Secret to Successful Relationships“When you’ve been rejected in love, not only are you engulfed with feelings of romantic love, but you’re feeling deep attachment to this individual,” says anthropologist Helen Fisher in a 2008 TED talk on the brain in love. “Moreover, this brain circuit for reward is working, and you’re feeling intense energy, intense focus, intense motivation and the willingness to risk it all to win life’s greatest prize.” In other words, you—like Gatsby—are obsessed with winning this person’s heart.The rejection we feel when our love is not returned causes huge emotional turbulence and even physical pain. But against all odds, we stay hopeful. The mere possibility that the person we love might one day love us back keeps our attraction alive.In fact, any shred of uncertainty only fuels the fire. As a 2011 study showed, we feel most attracted to someone when we’re not sure if they like us or not. We wind up thinking about that person more often, wondering how they feel or how to attract them, and the authors believe that may lead us to think we’re in love.MORE: Are You Dating a Commitment-Phobe?On top of that, the myth that there is only one person out there for you—a single, magical soul mate—raises the stakes on unrequited love. “People often think they’ve found their soul mate,” says Rachel Sussman, a Manhattan-based relationship therapist and author of “The Breakup Bible.” “If they’re sold on the idea that there’s only one person for each of us, they really tend to feel that they’ve lost that one opportunity.”Of course, the fallacy of that is obvious, unless you’re too blinded by what feels like love to see it. “If they really were your soul mate, they would be with you,” Sussman adds. But if believing that was so easy, we would all move on a lot faster.Letting go is tough. It’s a prolonged battle between your logical brain and your instinctive one. Since love mirrors all of the patterns of addiction—obsessive thinking, cravings, distorted reality, withdrawals, relapse—you literally need to wean yourself. “Create as much distance as you possibly can,” Sussman says. “Discontinue contact, stop talking about [the person] and don’t go on their Facebook page.” Those little check-ins only make it worse and harder to let go.MORE: How to Put Your Breakup Behind YouMost of all, stop indulging any stories about the person or what your relationship would be like if you were together. “You’ve got to poke holes in the fantasy,” Sussman says.To do that, list the person’s negative qualities or catalogue everything you don’t know about them. Imagine bickering over your finances or childcare, and remember that this person would have flaws just like any other person.Once you convince yourself that the fantasy isn’t real, moving on will take an ego boost. “Constant rejection chips away at self-esteem,” Sussman says. “Especially if it’s already underdeveloped.” Build self-confidence by taking interesting classes such as yoga, cooking or language lessons, traveling, volunteering or focusing more on excelling at your career. Not only will those distractions help you forget the person and feel better about yourself, they’ll also give you opportunities to meet new people.If you want to find love, you need to let go of a fantasy that is holding you back, and know this truth: There are other people out there, ready to love you back.QUIZ: How Confident Are You?