When people spend most of their lives sitting, over time their physical bent over posture starts to feel normal. Better posture means better alignment, with head, torso and pelvis stacked in a line over your feet.
Floor Posture Test
Lie flat on a carpeted floor and then notice:
Posture Stretch to Lengthen to Stand Taller
Being aware is the first step to fighting back and improving your posture.
Especially if your head is in a forward head posture, muscles and ligaments have likely shortened over time.
Next time you take a Posture Break to lengthen, turn a page or two to make the book support a bit thinner. See how close you can get to aligning your head, torso and pelvis for a stronger posture.