The only genuine good that life can yield a man is the free possession of his own soul
 William James, The Varieties of Religious Experience (1902). copy citation

Context

“strong happiness is always linked with pain; therefore hug the safe shore, and do not tempt the deeper raptures. Avoid disappointment by expecting little, and by aiming low; and above all do not fret.” The Stoic said: “The only genuine good that life can yield a man is the free possession of his own soul; all other goods are lies.” Each of these philosophies is in its degree a philosophy of despair in nature's boons. Trustful self-abandonment to the joys that freely offer has entirely departed from both Epicurean and Stoic;” source