Most people have an upside down view of the design of the body. It isn’t unreasonable. You would think that the head sits down on top of the spine, the shoulder girdle on top of the rib cage, pelvis on top of the leg, etc, and to some degree this is obviously true.
But the body is really a series of hanging structures from the head down. Your shoulder girdle (collar bones and shoulder blades) only connects to the rib cage in one place, where the collar bone meets the rib cage. Other than that it should sit suspended over the ribs cage, hanging from muscles that connect it to the head.
The arm is designed to hang from the shoulder and should never be fixed in place which is unfortunately what happens with many yoga and postural instructions. Even the lower leg hangs from the pelvis in its way. The hamstrings and quadriceps attach to the pelvis and then below the knee essentially suspending the shin from the pelvis.
Try moving through your day is if a puppeteer were pulling your strings and lifting you up out of your body.