Libido is the ongoing appetite for sex. It rises and falls with health, stress, hormones, newness, and whether you like the person in the other chair. A high libido is not virtue. A low one is not a defect. Trouble starts when the level you have and the life you want refuse to meet.

Partners compare frequencies and take the gap personally. Sometimes it is personal: resentment is a powerful antilibidinal drug. Sometimes it is a thyroid, a pill, a baby, a depression. Sorting those piles is more useful than keeping score.

You can have a strong libido and still not want a particular partner. You can have a quiet libido and still want that partner close. Desire for sex and desire for a person overlap without being identical.

If the drop is sudden and scares you, a checkup is a reasonable first date with the problem.