An archer competing for a clay vessel shoots effortlessly, his or her skill and concentration unimpeded. If the prize is changed to a brass ornament, the hands begin to shake. If it is changed to gold, he or she squints as if going blind. The abilities do not deteriorate, but belief in them does, as he or she allows the supposed value of an external reward to cloud the vision.
ZhuangziThere is danger for the eye in seeing too clearly, danger for the ear in hearing too sharply and danger to the heart from caring too greatly.
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