Aldous Huxley

 One third, more or less, of all the sorrow that the person I think I am must endure is unavoidable. It is the sorrow inherent in the human condition, the price we must pay for being sentient and self-conscious organisms, aspirants to liberation, but subject to the laws of nature and under orders to keep on marching, through irreversible time, through a world wholly indifferent to our well-being, toward decrepitude and the certainty of death. The remaining two thirds of all sorrow is homemade and, so far as the universe is concerned, unnecessary.