First adjust your cross! The connecting line between Baihui and perineum is perpendicular to the ground, perpendicular to the connecting line of shoulder well, and on the same plane.

You can do this by pushing your neck, retracting your jaw (the dumb door opens backwards), slightly expanding your shoulders (the clavicle is naturally flat), and retracting your abdomen and buttocks, that is, opening your life door backwards and retracting your tail (the coccyx is tilted forward to the tip of your nose).