What is a desire discrepancy, and how common is it?
A difference between partners in how much sexual intimacy each wants. It is close to universal in long relationships, and the distress it causes usually comes less from the difference itself than from what each partner concludes it means.
Why it is normal. Desire varies with health, medication, stress, sleep, hormonal changes, mental health, age, life stage and the relationship's own state. Two people's curves will not track each other, and periods of mismatch are the statistically ordinary condition rather than a sign of incompatibility.
The distinction that helps most. Research distinguishes spontaneous desire — arriving unprompted — from responsive desire, which emerges after intimacy has begun in a context that feels good. Many people, disproportionately though not exclusively women, experience desire mainly as responsive. A partner who expects spontaneous desire and does not experience it may wrongly conclude something is wrong with them or the relationship. The model of waiting to feel like it before starting simply does not describe how many people work.
Why it becomes painful. The higher-desire partner frequently interprets refusal as rejection of them personally. The lower-desire partner frequently experiences any affection as a request, and begins avoiding touch entirely to avoid the implied question. This is the trap: physical affection disappears, both feel worse, and the cycle tightens.
What tends to help:
Separating affection from initiation explicitly, so a hug is not a proposal. This one change resolves a surprising amount.
Understanding context, since desire responds to the conditions around it — rest, privacy, resentment, workload — far more than to effort.
Talking about it outside the bedroom, and outside the moment of refusal.
Curiosity rather than diagnosis. "What makes you feel like it?" is a more useful question than "why don't you?"
Ruling out medical causes — thyroid, hormones, pain conditions, and very commonly antidepressants and hormonal contraception, all of which are discussable with a doctor.
A therapist with specific training, where the pattern is entrenched.
When it is not just a discrepancy: persistent pressure, obligation, or sex used as leverage is a different problem and is about coercion, not desire.