The beginning of a relationship is its own drug. There’s the novelty, the anticipation, the constant gravitational pull toward another person. Sex is frequent and charged with an electricity that feels, in the moment, like it couldn’t possibly wear off. And then, after some time, it just…does.

Most people reach for the simple explanation: novelty. It’s not new anymore, so it’s not as exciting. True, as far as it goes. But according to therapists and psychologists who work with couples, the full picture is considerably more complicated than that.

Somatic therapist Briony Montgomery, speaking with Body+Soul, has a theory that takes a second to land. Feeling safe, truly safe, with another person can actually suppress desire. The nervous system, which spent the early months of the relationship running on adrenaline and anticipation, suddenly has nothing to scan for. “When your body is constantly scanning for what might go wrong, it’s very difficult to drop into pleasure,” she says. Take away the threat, and sometimes the charge goes with it.

Psychologist Taash Balakas gets at something related. For people who’ve spent years running on self-reliance, usually because dependable support was never really on offer, being cared for can feel more threatening than comforting. “Research shows that people who fear being cared for also report higher anxiety and stress,” she says. “It’s not about pride, it’s about protection.” And a nervous system running on low-grade anxiety isn’t exactly primed for getting it on.

Losing someone you’ve been seeing for two months is painful. Losing someone whose name is on your lease, who knows your family, who you’ve built an entire daily life around, is something else. The body treats those two scenarios very differently, and desire gets caught in that gap.

Balakas has a prescription, and it’s deceptively simple. “Softening doesn’t mean losing your independence,” she says. “It means allowing yourself to experience care without assuming it will disappear.” Anyone who’s spent years bracing for abandonment knows how much work is hiding inside those two sentences. And for many people, letting someone take care of them turns out to be far more exposing than anything that happened in the early months.