My Dear Friend,
My Tannhäuser is reposing, and I feel little impelled to rouse him. It is true I have begun the composition, but not enough to be worth speaking of! I lack two things—quiet and what I can only call ease. I am not at ease, that is to say my mood is inwardly and outwardly discordant. I am distrait and long for rest—I don't mean the rest of the sluggard, but, on the contrary, a concentrated restlessness. I want to think about a few things, not about all sorts of things. But probably many years will pass before I can get this harmonious rest, for I have to make up for ten years of my past. [...]
Source: Letters of Richard Wagner, Vol. 1, selected and ed. Wilhelm Altmann, trans. M. M. Bozman (J. M. Dent & Sons, 1927), No. 98