The point, which can hardly be repeated too often, is that differentiation is not separation. The head and the feet are different, but not separate, and though man is not connected to the universe by exactly the same physical relation as branch to tree or feet to head, he is nonetheless connected - and by physical relations of fascinating complexity.
Sometimes in life, things happen that will knock you back. Hell, you may get beaten to your knees but you must never ALLOW this world to knock you down! Conjure up all the strength you have and drive through whatever it is keeping you on your knees. Build up the strength and your knees may never buckle again!
When a resolute young fellow steps up to the great bully, the world, and takes him boldly by the beard, he is often surprised to find it comes off in his hand, and that it was only tied on to scare away the timid adventurers.
The point, which can hardly be repeated too often, is that differentiation is not separation. The head and the feet are different, but not separate, and though man is not connected to the universe by exactly the same physical relation as branch to tree or feet to head, he is nonetheless connected - and by physical relations of fascinating complexity.