Closeness is not the same thing as heat
A therapist noticed her most connected clients often had the least interesting sex, and set out to explain why.
Esther Perel's clients kept describing a version of the same problem: they'd built exactly the closeness self-help books recommend — safety, honesty, total familiarity — and their desire had gone quiet anyway. She started to suspect the advice had it backward.
Her argument in Mating in Captivity is that desire and intimacy don't run on the same fuel. Intimacy craves certainty: knowing your partner, being fully known. Eroticism runs on mystery, risk, a bit of the unknown. Perel writes that increased emotional closeness is, for many couples, accompanied by decreased sexual desire, not despite the intimacy but partly because of it. Merge two people completely and you remove the separateness that makes wanting someone across a distance possible.
Her counterintuitive advice: stop treating total transparency as the goal on its own. Protect some part of yourself as still yours, still a little unknown, even to the person who knows you best.
The couples with the most heat, in her clinical experience, aren't the ones who erased the space between them. They're the ones who kept some of it on purpose.