Yoga Nidra is often described as sleep, which is misleading. The practice sits deliberately at the boundary: the body is as relaxed as it is in deep sleep while attention remains awake. The traditional name, yogic sleep, points at exactly that contradiction.
It is done lying down, in savasana, usually with support under the knees and a light covering, since body temperature drops. A voice guides attention systematically around the body — right thumb, index finger, middle finger, and so on through every part — while the practitioner does nothing but follow. The rotation is not arbitrary; it follows a fixed sequence that the mind eventually learns.
What makes it useful is precisely that it asks for no effort. Meditation practices that require concentration are difficult on the days you most need them. Yoga Nidra requires only that you stay awake and listen, which is achievable when concentration is not.
Twenty to thirty minutes is a full practice. Practitioners commonly report that it leaves them rested in a way that a nap of the same length does not, and the classical claim — that a period of Yoga Nidra corresponds to a considerably longer period of ordinary sleep — is at least consistent with what people describe.
The best time is late afternoon or early evening, and not immediately after a heavy meal. If you fall asleep during it, that is not a failure; it usually means the practice found what your body actually needed.