adjusting expectations, telling themselves it probably doesn't matter as much as it feels like it does. And the distance grows.
What therapy can offer
In therapy we can explore what has shifted, and why. Sometimes it's resentment that hasn't found a voice. Sometimes it's anxiety — performance anxiety, or a more diffuse anxiety about vulnerability and being seen.
Sometimes it's the way long-term intimacy gradually changes the erotic: the very safety and familiarity that makes a relationship sustaining can, paradoxically, work against desire, which tends to thrive on a degree of distance that coupledom makes harder to sustain.
Desire is not a fixed quantity that either exists or doesn't. In most people it is something more like a capacity — one that responds to conditions, and that can be cultivated, recovered, and sometimes discovered anew. The aim is to move away from sex that feels like obligation or a test the relationship is quietly failing, and toward something that feels, again or perhaps for the first time, like it genuinely belongs to you both.