Some relationships end like a gradual descent into madness. At least, that’s how the end came to Brooke*. From the start, her relationship with Jon was one of the most amazing, intense relationships she’s ever had. They felt like equals, saw eye to eye, fell head over heels in love—the physical attraction was “delicious.” Then, five months into the relationship, she told him that if he ever wanted to move in together, she’d be “totally down.”So began an excruciating end.Over the next few months, with no explanation (and no moving in together), he stopped saying ‘I love you,’ retreated into a shell and shut her out. “It was like a slow-motion heartbreak,” she recalls. “I didn’t understand what was going on.”MORE: Are You Dating a Plate Spinner?One afternoon, crying on his couch, she begged him to explain, to give some indication of why his feelings changed. “I don’t know what you’re talking about,” was all he had to say. She wondered if she was going crazy, but she knows she didn’t imagine what he did next: “He put his hand over my heart, my upper chest, and just very slowly pushed me out of the apartment. He kept one hand on my chest as he opened the door and literally pushed me out.” As he closed the door, she collapsed. “I couldn’t breathe. I remember just covering my eyes and walking out to the street and wanting to evaporate, wanting to absolutely disappear.”Most of us, like Brooke, have had our true feelings dismissed by someone we cared about. Perhaps your experience was less dramatic—your partner often said you were overreacting, or insisted you had a roving eye—but no matter the severity, your partner may have been gaslighting you.If so, learning to spot this kind of crafty manipulation will change your life.The Gaslighting EffectIngrid Bergman made Brooke’s experience famous, long before Brooke was even born. In the 1944 thriller, “Gaslight,” Bergman plays a woman whose husband is trying to convince her she’s crazy. He makes objects disappear and claims she took them or makes the gaslights dim and brighten for no reason. All the while, he convinces her that what she believes is true (that she didn’t take the objects and the lights are dimming) is a figment of her imagination.Since then, ‘gaslighting’ has become part of the vernacular, describing a method of psychological manipulation where the victim comes to doubt the reality of his or her own experience, much like Brooke came to doubt that her perception of Jon’s distance was real or her feelings of loss were valid.In a gaslighting relationship, one person states his or her case with so much certainty and regularity that the victim starts to wonder if it might in fact be true. “It’s not just saying ‘I’m certain,’” says Dr. Robin Stern, psychologist and author of “The Gaslight Effect.” “It’s saying, ‘I’m certain and you don’t know what you’re talking about.’” As a result, the victim is thrown off balance. “Your own confidence and sense of reality is compromised. You can no longer find your center or have confidence in your reality.”It’s an insidious tactic, to say the least.Unfortunately, gaslighting can be easy to pull off when there’s an imbalance of power. The perpetrator could be a boss or parent, an idealized partner or the popular girl in high school. Even therapists can easily become the bullies, particularly when a patient feels ready to leave therapy and the therapist says, ‘You’re not ready. This is resistance.’ “Because you’ve given this person power, you have a stake in believing them,” explains Stern. You wonder, ‘Why would my mom lie to me?’ or ‘Why would my therapist mislead me?’ And slowly, you start to accept their reality.In many cases, gaslighting is also an expression of contempt, where one partner attacks the other with an air of superiority. “Contempt is found in sarcasm, mocking and put-downs,” explains Dr. Bob Navarra, MFT, a certified Gottman couples therapist. “It’s the position that you are crazy for feeling the way you do, that there is something wrong with you.”It’s the single biggest predictor of separation and relationship unhappiness.Elena, 38, fell prey to that statistic. She’s not sure why she married Brett in the first place, though after living together for six years, friends and family expected it and “it was something to do.” Even before the wedding, she knew she’d made the wrong choice.QUIZ: What’s Your Relationship Style?Not long after the wedding, she told Brett that she wanted to break up. “I told him all the typical things,” she says. “That I was unhappy, that I wanted to be in charge of my own life again, that I didn’t see any kind of good future for us and that we were only holding each other back.” She even admitted she’d cheated. He ignored everything she said and blamed it on “depression.”As she pushed to separate, he created a narrative that she was self-destructive, reckless, an addict. “On my birthday,” she recalls, “I went out drinking with my friends (as I do on my birthday) and was hung over the next day. He claimed that my alcoholism was out of control and that he ‘didn’t know what I would do next’ but suggested I would try to commit suicide or get arrested.”He painted himself as her savior, as someone trying to salvage the life she was trying to ruin, going so far as to call up her family members to tell them about her ‘addiction problems’ and ‘self-destructiveness.’ She eventually started wondering if she was just in denial—a worry her friends fortunately allayed.A Tale of Two RealitiesFor Elena, she and Brett lived in separate realities. In hers, she’d known their marriage was a mistake from the start and wanted out. In his, the marriage was fine and she needed help for what he likely experienced as a rather sudden change of heart.Navarra finds that couples often experience separate realities—after all, we all live in the confines of our own imaginations—and struggle to understand or acknowledge the other’s viewpoint. “We all have our own histories, experiences and perspectives that create our realities,” says Navarra. “When partners have different perceptions, they need to take the position that both realities are right; there isn’t one truth.”COLUMN: How to Have a Secure RelationshipWithout clear communication, it’s hard to access someone else’s reality, especially when one partner is emotionally expressive and the other shies away from emotion. “The emotionally expressive wife will get better responses from her husband if she is careful to avoid criticizing her partner’s lack of emotional responsiveness,” says Navarra, noting that the reverse is also true. “She should focus instead on her own feelings and what it is that she wants, without expecting him to have the same emotions.”More troubling—and truer to gaslighting in its purest form—is when one person no longer trusts his or her own intuition or feelings. When that happens, Stern recommends very simply getting back in touch with one’s own feelings by noting throughout the day, ‘I like this’ or ‘I don’t like that,’ and ‘this makes me feel good’ or ‘that makes me feel bad.’That exercise can help someone achieve the essential first step: recognizing that there’s a problem in the first place. “When people are physically abusive, you can point to it and say that’s an awful behavior,” says Stern. “But when someone is undermining your confidence and telling you different stories than you believe, you can’t always put your finger on it.”When doubt seeps in, a third party can be a lifesaver. “Talk to your friends, listen to them,” says Stern. “Running things by them if you’re not sure is a really wonderful way to stabilize yourself.”But she’s clear that when gaslighting becomes a defining pattern in the relationship, the only solution is the courage to walk away.Today, Elena is living happily on her own, traveling, getting in shape, and trying to revive her career. So is Brooke. She’s now in a happy, healthy relationship and has finally severed her ties with Jon, who came in and out of her life “like a ghost that just circled,” wreaking havoc for many years after they split. “It was like a cancer in me,” she says. “I think back and wish I could tell myself that my emotions were valid, to scoop myself up and give myself a big hug and say, honey, it’s not worth it.”MORE: How to Have More Self-Compassion*All names have been changed to prevent hate mail from any “crazy” exes.