Deeply revered man,
Only sentiments of the most intimate personal nature are in place on a day which has the distinction of being your birthday. Every one who has been brought in contact with you has had experiences which have affected him personally, in his innermost being. Such experiences cannot be added up into one great total, and were this possible, birthday felicitations in the name of the many would signify less than the most modest wish of the one.
It is now nearly seven years since I paid my first visit to Tribschen, and I know of nothing to say to you on your birthday more than this: since that time, I have regularly celebrated my spiritual rebirth in May of each year. Since that meeting, you live and work in me as unceasingly as a drop of blood, but one which, most assuredly, was not in my system previous to that time. This new element that had its origin in you incites me, makes me ashamed, encourages me, spurs me on and gives me no rest, so that I should almost feel inclined to be vexed with you for thus disquieting me, did I not feel that it is just this feeling of unrest that impels me and will eventually make of me a freer and better man. For this reason I can only be most deeply grateful to the man who has stirred these feelings to life in me, and my dearest wish for the approaching events of the summer is that you will have the same effect upon many others, who, seized by this same feeling of unrest, will thereby be permitted to participate in the greatness of your character and your career.
My only birthday wish for you today is that this may come to pass, for where is any other happiness that I could wish you? I beg you to accept this wish in the most friendly spirit from the mouth of your very faithful Friedrich Nietzsche.
Source: The Nietzsche-Wagner Correspondence, ed. Elizabeth Foerster-Nietzsche, trans. Caroline V. Kerr (Boni and Liveright, 1921), No. 49