Take a coin from your pocket and examine it. It has two sides, and each is different. There still is only one coin. If you could cut the coin in half, there would still be only one coin with two different sides. It is impossible to remove the parts from the whole. No matter how you try, the coin still remains the same coin with the same sides and the dividing of the coin does not make destroy the coin, it only changes its appearance.
It is the same with many things that appear opposite and different, sickness and health, wealth and poverty, love and hatred, living and dying, yin and yang. None of these things exist alone just as we do not exist alone. Each is part of a whole we call Tao, and each has its place and its time.
We can try all we can to change the course of the path, we can try with all of our strength to modify what is natural, we can deny till our last breath the oneness of the universe, but our effort and our words do not make the difference so. Just as the coin remains one coin, the Tao remains one Tao, life flows into death, flows into life again. Health flows into sickness eventually, even the sages caught a cold once in a while. Wealth and prosperity can be lost in a moment, only to be regained again.
If you study the symbol of yin and yang, there are no ridges or hard lines that separate one from the other, there is a pattern of flowing one into the other, this is the way of the Tao. The Tao is the source of everything, and the wellspring of nothing. It is the great fountain of life and energy, and everything returns to it. It is empty in appearance but the source of everything, and in its balance and flow there is peace and calm and power.
If you do not believe me, look into the ocean. Many things wash up on the beach, we did not ask to have them. Many people eat its fish and plants, it does not try to preserve them, A million creatures live and spawn and die there, it does not judge them. That is the picture of the flow and the balance. It is one way we may seek to understand the Tao.