Autopilot has preprogrammed destination and assumes that there are clear skies ahead. Oddly, breathing is set to a specific outcome which is instead conflict so it is necessary to reset and let breathing be used for relaxation instead of primal survival.
The Shape of Breathing
To recognize the shape-change that needs to happen imagine a bowling ball rolling back and forth in your pelvis (which is essentially a bowl). Adults normally breath up as if we are going to float away or pop so visualizing something heavy is helpful. The hardest thing to do after centering our breath in our lower body is to change the tension and shape of the abdominal and lower back muscles so again make the bowling ball heavy so as it rolls it carries some force with it.
Breathe in normally and then as you breathe out imagine the bowling ball being released at the top of your spine, rolling down the inside of your back. As you breathe in again the bowling ball rolls forward, out, and only slightly up, expanding your stomach out and up until the bowling ball slows and pauses as it reaches your sternum. On the way back down don’t press your stomach back in, let it stay round and relaxed. The bowling ball rolls back up your spine as you breathe in now pressing back, filling in the small of your back. With each breath out the ball rolls down settling your weight and rolls out and up expanding your shape. You can also do the same visualization side to side so you are eventually expanding/relaxing in all directions.
Afterwards take note of how your insides feel. Good breathing (even pausing to notice that you are breathing) is relaxing because it brings attention to the present but giving your organs a lot more space and a bit of a massage also adds to the benefits of deep breathing.