Sorrow and happiness are the heresies of virtue; joy and anger lead astray from TAO; love and hate cause loss of virtue. The heart unconscious of sorrow and happiness - that is perfect virtue. One, without change - that is perfect repose. Without any obstruction - that is the perfection of the unconditioned. Holding no relations with the external world, - that is perfection of the negative state. Without blemish of any kind, - that is the perfection of purity.
ZhuangziThere are no greater adversaries than yin and yang, because nothing in Heaven or on Earth escapes them. But it is not yin and yang that do this, it is your heart that makes it so.
ZhuangziThe birth of a man is the birth of his sorrow. The longer he lives, the more stupid he becomes, because his anxiety to avoid unavoidable death becomes more and more acute. What bitterness! He lives for what is always out of reach! His thirst for survival in the future makes him incapable of living in the present.
Zhuangzi