Once you have successfully tackled and subdued the over active mind (reduced its weight and influence) then the buoyancy of thymos (natural self as opposed to ego: unnatural self) depends largely on the support of the waist whose muscles, especially those either side of the lumbar spine, need to be strong. But it is not a usual muscular strength, which is one able to contract intermittently to deliver force, but one able to supply a steady stream of upward energy to balance the inexorable descent of gravity. When we walk and run the legs naturally pump such energy up the body, which is why these activities are often used to bring up the spirit. But when sitting we get no help from the legs so the heart tends to slump and the mind tends to get nervous and start chattering to itself ten to the dozen. When this happens it is far better to either get up and walk around or lie down flat to let the back rest.