In an entry from January of 1882 under the heading Sanctus Januarius, Nietzsche writes:
For the New Year—I still live, I still think; I must still live, for I must still think. Sum, ergo cogito: cogito, ergo sum. To-day everyone takes the liberty of expressing his wish and his favorite thought: well, I also mean to tell what I have wished for myself today, and what thought first crossed my mind this year,—a thought which ought to be the basis, the pledge and the sweetening of all my future life! I want more and more to perceive the necessary characters in things as the beautiful:—I shall thus be one of those who beautify things. Amor fati: let that henceforth be my love! I do not want to wage war with the ugly. I do not want to accuse, I do not want even to accuse the accusers. Looking aside, let that be my sole negation! And all in all, to sum up: I wish to be at any time hereafter only a yea-sayer!
As quoted on the Brainpickings blog