Here is a yoga posture to help relax the nervous system.
Sit on your mat with your legs extended in front of you.
Stretch your arms above reaching towards the sky. Bend forward slowly from the hips folding your upper body over your extended legs. Breathe. Relax into the stretch without putting undue pressure on the lower back. Breathe. Unfold slowly by engaging the abdominal muscles and pressing into your legs for an extra boost.
This calms the parasympathetic nervous system.
It is the opposite of the fight or flight mode we find ourselves in when feeling stressed.
Hope this helps.