Sleep onset needs a drop in core body temperature of roughly half a degree. That is why a warm room, a heavy duvet, a hot shower right before bed or a late workout keep you awake even when you're exhausted — and why a slightly cool bedroom is the single most reliable environmental change for sleep.

Swara Yoga maps the same thing onto the breath. The left nostril — Iḍā, the cooling, lunar channel — is the one the tradition associates with rest, and it holds that when the left flows, the body settles. Whether or not you take the map literally, the posture that opens it is worth having.

Lie on your right side. The pressure on the right side of the body shifts the nasal cycle toward the left nostril within a few minutes — you can usually feel it happen. Then lengthen the out-breath: in for four, out for eight, and let the counting go once the breath has moved.

Delve's Sleep Descent practice is built from exactly these three things: a cooler room, the right side, and a long exhale. If sleep is what you came here for, it's the last sitting of every week of your course.