[...] Rising from my work, I cannot let my quiet and solitary birthday pass without sending you, from the very depths of my heart, my most warm and grateful greetings. Having recovered from an illness, I found my work even dearer to me to-day, and I see clearly, and with certainty, that it is my greatest achievement. I am sure of its outward success. How could I enjoy this sense of gladness and exaltation without raising most sincerely thankful and appreciative eyes to you? And so, without knowing it, you have given me a splendid birthday present! When some day you hear the prelude to the third act (I often depart from serial order as I work), and then the chorus with which the people enthusiastically receive Hans Sachs, [...] be sure you remember what frame of mind I was in on this birthday of mine! [...]
Source: Letters of Richard Wagner, Vol. 2, selected and ed. Wilhelm Altmann, trans. M. M. Bozman (J. M. Dent & Sons, 1927), No. 530