In a long-term relationship, many issues can arise over time. Among these are poor communication, changes in expectations, or plain dissatisfaction. But one thing seems to be incredibly common, yet not as openly discussed—the diminishing sexual desire.

Why do couples who were once so smitten with each other lose this spark? Does it mean that their love is gone? Psychotherapist Esther Perel decided to examine this phenomenon and find answers. She explored the intersection of emotional security and eroticism by looking at different couples, from straight to gay and from young to old.

She found that love and desire are not mutually exclusive but can pull us in different directions. We want passion and mystery, but also need security and predictability. Many people may eventually give up on the erotic aspect of their relationship, believing that it’s just the way life goes. The fire that was burning bright and making life exciting starts to die down. Still, is there a way to rekindle that flame?

As Perel states, “Fire needs air; desire needs space.” When two partners get used to each other, it becomes increasingly hard to find each other desirable. Instead, they need to work on gaining a new perspective. For example, Adele, Perel’s client, had a moment that led her to that realization.

Adele was happy with Alan, her husband of 7 years, but she lacked excitement. It wasn’t as much about the sex, more about making each other feel special, like it was in the beginning. Perel advised her to bring a sense of the unknown into a familiar space, to zoom out and see Alan “with new eyes.”

When Alan and Adele were visiting a work function, such an opportunity presented itself. Adele saw Alan talking to some colleagues and suddenly was able to look at him in a new light. She saw him as an attractive, intelligent, and well-spoken man instead of zooming in on his flaws or replaying old arguments. By taking him out of the context of their marriage, she was able to reignite her attraction to him.

Believing that one knows everything there is to know about one's partner is a misconception. People are not static; their unique qualities can shine through different contexts. That’s why couples in long-term relationships shouldn’t rely on or get annoyed by each other’s predictability.