That is why the word dui is so important. It reminds us that opposites are not mutually exclusive but are actually pairs. If we have sadness, then happiness will come too. If we have love, we will also have to deal with conflict. For all our learning, we will have days where our philosophical outlook will be tried to its breaking point. For all the peace of meditation, we will still have to face work, illness, and stress. There is no way in life that only stands on one side of a pair and never ventures into the other. The sooner we accept — and work with that — the better off we will be.
That is why the way of Tao is the middle way. We cannot have one side without the other in life: it is wisdom to strike a balance between them both.
— Deng Ming-Dao, Everyday Tao