If I had to choose the most comforting of yoga poses, I'd instantly say Child's Pose, or Balasana. Nothing says complete surrender like grounding to your knees and drawing your head to the earth. Something beautiful happens when you arrive in this pose. Everything stops around you. The mind quiets, the breath slows, tension releases. It can be quite exquisite.
This pose is deeply calming. I suggest taking it anytime you feel you "need a break". Physically, this can come at a time in our asana practice when we've used a lot of energy, after Sun Salutations or backbends, or moments when you want to connect with the sensations within your deepest Self. But for times when your yoga has come off the mat or if you have the time for just one pose, choose Child's Pose. When your feeling too stimulated or overwhelmed, when your body, mind, or spirit are tired, when your full with grief or gratitude, when your lost, when your delighted. It all comes back to turning deeply within to the well of peace and beauty at your center.
Extended Child's Pose (Balasana Variation)
Sit the hips back toward the heels. Extend the spine forward over the thighs, as the hands extend out in front of you, about shoulder width apart.
Slowly draw your forehead to the earth (or a block, book or pillow. Make yourself supremely comfortable!)
If your breath feels restricted at all, gently open the knees toward the edges of the mat (as I've done in the image above), toes still touching. Make space for the belly and rib cage.
Remain here for several breaths, as feels comfortable for you. For deep restoration, move towards 10-20 breathes. ***Remember to always respect your body's abilities and limitations. Come out of the pose immediately if you experience discomfort or pain.***