Here's a little trick I just discovered, which you might want to try if you're like me and have horrible posture:
Next time you're dealing, and your neck and shoulders are feeling terribly stiff and tight, and you want to stretch while in the box...think of this guy:
Remember, in the movie, the horse takes a few steps, and this guy stretches his neck straight up? Put yourself in his shoes. Push down with your hips, straighten your spine, pull your shoulders down and back, lift your neck.
It feels amazing.