At every step one has to wrestle for truth; one has to surrender for it almost everything to which the heart, to which our love, our trust in life, cling otherwise. That requires greatness of soul: the service of truth is the hardest service. What does it mean, after all, to have integrity in matters of the spirit? That one is severe against one's heart...that one makes of every Yes and No a matter of conscience.

Nietzsche: Philosopher, Psychologist, Antichrist (ed. 1968)