It happens eventually to every long-term couple. In the beginning of your relationship, you craved to be with each other constantly. It was exciting and intimate. And now, it isn't. Even the most loving relationships reach a point when everyday life takes priority and the relationship moves to the back burner. But this doesn't have to mean that your relationship is doomed to bed death. You can still reclaim that old spark.

Belgian psychotherapist Esther Perel is on a mission to educate couples about maintaining sexual desire in long-term monogamous relationships. She suggests that relationships require distance in order to fuel desire. "Can we want what we already have?" she asks in her TEDx talk. Perel identifies a distinction between love and desire, claiming that it is possible to love your partner without desiring them. However, she believes that desire is a central concept of modern love, and that in order to sustain desire in a committed relationship, a couple must reconcile their contradicting needs for security and novelty. But if love requires closeness and desire demands space, how can a couple overcome that contradiction together?

While on tour promoting her book Mating in Captivity, Perel surveyed people across genders, religions, and cultures, asking them to name a time when they felt most drawn to their partner. One of the most common responses was that they felt most drawn to their partner when their partner was self-sustaining and confident in their own element. According to Perel, it is in these moments that a familiar partner becomes unknown once again, a mystery begging to be solved. This is what propels couples towards each other and sustains excitement and desire in a long-term relationship.

"Mystery is not about traveling to new places, it's about looking with new eyes," Perel claims. In order to gain a perspective that enables mystery, both partners in a relationship must be free to experience autonomy. Each partner must have the opportunity to foster an identity that is not defined by their relationship. They must be able to explore new interests, hobbies, and friendships while still knowing they are secure in their relationship. The death of erotic intimacy, Perel explains, occurs when one or both members of a couple is forced to give up either their need for connectedness or for freedom. If one partner is too afraid to give the other space to explore, then the second is forced to choose: they must either give up their autonomy in favor of closeness, or they must give up that closeness in order to experience autonomy. Either way, they lose a vital part of their relationship.

Perel identifies a behavior of erotic couples who are able to reconcile their fundamental needs for closeness and autonomy: they maintain sexual privacy. "They understand that there is an erotic space that belongs to each of them," she explains. This erotic space allows each person to accept and embrace their own sexuality, instead of carrying the weight of their responsibilities into the bedroom with them. When each person has the room to fully explore their own sexuality, they discover mysteries within themselves. And through these personal explorations, they can share their mysteries with each other.

Ultimately, erotic success in a long-term relationship requires trust. Each partner must feel comfortable allowing the other to explore themselves as an individual. By fostering a space where each partner has the freedom to journey alone while still feeling safe and secure in their relationship, a healthy distance is allowed to grow. That distance is the key to sustaining desire.