Downward Dog, to me, is truly a cure-all pose. For the purposes of stress relief, we look to the inversion aspect of this posture as a way to calm and soothe the brain, the eyes and the nervous system.
From a hands and knees position with the knees under the hips and the hands under the shoulders, walk the hands another hands length out in front of you, spread the fingers well and claw at the floor with the hands, as you begin to lift the knees and send the buttocks high into the air. Press the energy and weight back into your legs and start to fully extend the legs (if this is not possible because of calf or hamstring tightness keep the knees bent). Lift the buttock bones HIGH into the air and release the weight of the head through the arms. Breathe slowly and deeply through your nose. Stay for up to one minute, then slowly lower the knees and rest down for a few breaths.