The body is composed of a series of building blocks, one on top of the other. The head is the topmost building block. It rests on the neck building block, and so forth down to the foot building block. Gravity pulls the building blocks down. We feel heavy and tired because the building blocks are not aligned perfectly. For example, if our head is forward we are constantly fighting against gravity. However, if the building blocks are aligned such that none of them are leaning forward or to one side, then there is a straight line of gravity pulling from the top of the head down through the middle of the foot. In such a case the building blocks are perfectly stacked and the body feels … weightless.