When Lisa Phillips was thirty years old, she fell passionately in love with an unavailable man. Her crush began as a hopeful mental diversion, but quickly escalated into a kind of madness. At one point, she found herself standing outside the man’s door, knocking so loudly and insistently that when he finally opened it he was holding a baseball bat and threatening to call the police.

“As the months passed and he didn’t come around, something inside me shifted. My unrequited love became obsessive. It changed me from a sane, conscientious college teacher and radio reporter into someone I barely knew—someone who couldn’t realize that she was taking her yearning much, much too far,” Phillips writes in her fascinating new book, Unrequited: Women and Romantic Obsession.

For Phillips, a journalism professor at the State University of New York at New Paltz, the lunacy was relatively short-lived. Eventually, she fell in love with someone else, and they later married and had a daughter. But when she was recovering from her heartache, she promised herself she would one day re-examine that infatuation and try to make sense of out it.

Crushes, as we all know, are an enormous waste of energy—all the time we spend daydreaming about our beloved is time that we’re checked out of our actual lives. They make us fall behind at work, ignore our friends (or drive them nuts with our endless monologues about him or her) and, worse of all, fail to notice nice people who might actually like us back.

But most of us do fall under the spell of someone who doesn’t return our affections at some point; Phillips says that 93% of us have been rejected by someone we loved passionately.

Although unrequited love is extraordinarily painful, Phillips says it can also have a beneficial side. She recounts the story of Diane, whose crush on a co-worker from Mexico prompted her to end a bad relationship, learn Spanish, redecorate her home and plant zinnias in her yard. She didn’t get the guy, but she did move forward.

“Unsatisfied desire—those distracted, bittersweet days of seeing your beloved glitter with not yet—are worth something even if they result in nothing. In the days of unsatisfied desire, we did feel more alive as we explored our new place for ourselves in the world through our desire for another. We planted zinnias, we opened up about our lives and we daydreamed about an emotional utopia. We lived in the suspense of ‘Do you love me?’ and myriad other questions that passion brings forth, questions about fear, aloneness, possibility, and what it means to be human,” writes Phillips.

Reading Unrequited reminded me of the time, many years ago, when I was tortured by a crush. It was terrible to be in love with a man who had no interest in starting a relationship with me, and I still cringe when I think of the brainspace I lost to my obsession.

But, like Diane, I also started making important changes in my life during that time. I ended a relationship that wasn’t working. I moved to a better apartment. I took acting lessons and yoga classes. I threw parties, honed my public speaking skills, and developed my upper-body strength.

Of course, the idea was to become a woman who this particular man would love, and at that I failed completely. But in the process, I achieved something more important: I started to become the woman I wanted to be. I began to see through all of the cultural garbage I was putting on myself—not pretty enough, smart enough, sweet enough, etc. And I began to have faith that one day I’d meet a great guy who loved me as much as I loved him. And that’s exactly what happened.

Sara Eckel is the author of It’s Not You: 27 (Wrong) Reasons You’re Single. You can get a free bonus chapter of her book at saraeckel.com. You can also find her on Twitter and Facebook.