Compose

"je größere Fortschritte in der Kunst man macht, desto weniger befriedigen einen seine ältern Werke."
'The greater progress you make in art, the less satisfying your older works become.'
Beethoven to Friedrich von Matthisson in Dessau, Vienna, 4 August 1800 (BGA 47).  
Beethoven-Haus Bonn, facsimile of the lost autograph

"ich kann gar nichts unobligates schreiben, weil ich schon mit einem obligaten accompagnement auf die Welt gekommen bin."
'I can't write anything unobligatory because I was born with an obligatory accompagnement.'
Beethoven to Franz Anton Hoffmeister in Leipzig, Vienna, 15 December 1800 (BGA 49).
Beethoven-Haus Bonn, NE 181

"Ich lebe nur in meinen Noten, und ist das eine kaum da, so ist das andere schon angefangen, so wie ich jezt schreibe, mache ich oft 3 4 sachen zugleich -"
'I only live in my scores, and when one is barely there, the other has already begun, the way I write now, I often do 3 4 things at the same time -'
Beethoven to Franz Gerhard Wegeler in Bonn, Vienna, 29 June 1801 (BGA 65).
Beethoven-Haus Bonn, Collection Wegeler, W 17

"und man muß nicht so göttlich seyn wollen, etwas hier oder da in seinen Schöpfungen zu verbessern"
'and you don't have to want to be so divine as to improve something here or there in your creations'
Beethoven to Breitkopf & Härtel in Leipzig, Vienna, 4 March 1809 (BGA 359).
Beethoven-Haus Bonn, NE 205

"Melodie ist das sinnliche Leben der Poesie."
'Melody is the sensual life of poetry.'
Attributed. This quote is taken from a letter from Bettina Brentano (later married to von Arnim) to Johann Wolfgang von Goethe dated 28 May 1810. In it, she describes her impressions of Beethoven and puts the above words into his mouth - it is therefore doubtful whether Beethoven really expressed himself in this way.
Arnim, Bettina von: Goethe's Correspondence with a Child, vol. 2, Berlin: 1835, p. 196

"Deine Zeit vergeht geschwinder, rollt schneller um, als die wo wir unsern Geist oder ich mich mit meiner Muse beschäftige."
'Your time passes more quickly, rolls round faster than the one where we occupy our minds or I occupy myself with my muse.'
In his diary, 1812-1818.
Beethoven's Diary: 1812-1818, ed. by Maynard Solomon, Bonn: Beethoven-Haus, 2nd edition, 2005, p. 42  

"Ich habe immer ein Gemälde in meinen Gedanken, wenn ich am Komponieren bin, und arbeite nach demselben."
'I always have a painting in my mind when I'm composing, and I work according to it.'
Inscribed. Allegedly in 1815 to Charles Neate.
Thayer, Alexander Wheelock: Ludwig van Beethoven's Life. Volume 3, Berlin, 1871, p. 506

"Kommen Sie an die alten Ruinen, so denken sie, daß dort Beethoven oft verweilt, durchirren sie die heimlichen Tannenwälder, so denken sie, daß da Beethoven oft gedichtet, oder wie man sagt componirt"
‘If you come to the old ruins, you will think that Beethoven often stayed there; if you wander through the secret pine forests, you will think that Beethoven often versed there, or as they say, composes'
Beethoven to Nannette Streicher in Baden, Vienna, 20 July 1817 (BGA 1142).
Original not known; text according to TDR IV, p. 487 f., no. 12

"ich schreibe lieber 10000 Noten als einen Buchstaben"
'I'd rather write 10,000 scores than one letter'
Beethoven to Nikolaus Simrock in Bonn, Vienna, 28 November 1820 (BGA 1418).
Beethoven-Haus Bonn, Collection H. C. Bodmer, HCB Br 233

"Ich hoffe noch einige große Werke zur Welt zu bringen, u. dann wie ein altes Kind irgendwo unter guten Menschen meine irdische Laufbahn zu beschließen."
'I hope to bring a few more great works into the world and then, like an old child, to end my earthly career somewhere among good people.'
Beethoven to Franz Gerhard Wegeler in Koblenz, Vienna, 7 December 1826 (BGA 2236).
Tokio, Nanki Music Bunko, Oki-Collection, Sign. L 2  

"sie kommen ungerufen, mittelbar, unmittelbar, ich könnte sie mit Händen greifen,"
'they come uncalled, indirectly, directly, I could grasp them with my hands,'
Attributed to. A report by Louis Schlösser on Beethoven's alleged answer to the question of where he got his ideas from.
Schlösser, Louis: Memories of Ludwig van Beethoven (conclusion), in: Allgemeine deutsche Musikzeitung, Vol. 7, No. 52, 24 December 1880, pp. 413-417

"So pocht das Schicksal an die Pforte!"
'This is how fate knocks at the door!'
Attributed. According to Schindler, this is how Beethoven is said to have characterised the theme of his 5th Symphony - the C minor Symphony owes its nickname 'Symphony of Fate' to this anecdote.
However, the authenticity of this statement may be questioned, as it was penned by Anton Schindler, an early Beethoven biographer. Schindler knew Beethoven in the last years of his life and tried to profit from the master's fame by claiming to be the only authentic reporter of Beethoven's life and even testifying to events that he could not possibly have witnessed.
Schindler, Anton: Biography of Ludwig van Beethoven: with a portrait of Beethoven and two facsimiles, first edition, Münster: Aschendorff, 1840, p. 241

"Von Herzen - Möge es wieder - Zu Herzen gehn!"
'From the heart - May it go to the heart again!'
Motto on the autograph of the Mass in D major for four solo voices, choir, orchestra and organ ('Missa solemnis') op. 123.
Berlin, Staatsbibliothek, Mus.ms.autogr. Beethoven, L.v. 35,25  

"Ich trage meine Gedanken lange, oft sehr lange mit mir herum, ehe ich sie niederschreibe"
'I carry my thoughts around with me for a long, often very long time before I write them down'
Attributed to. A report by Louis Schlösser on this alleged statement by Beethoven.
Schlösser, Louis: Memories of Ludwig van Beethoven (conclusion), in: Allgemeine deutsche Musikzeitung, Vol. 7, No. 52, 24 December 1880, pp. 413-417

"Ach Unsinn', sagte er [Beethoven], 'ich habe nie daran gedacht, wegen Ruhm und Ehre zu schreiben. Was in meinem Herzen ist, muß heraus, und deswegen schreibe ich."
'Oh! nonsense,' he said, 'I never thought of writing for fame or honor. What is in my heart must come out, and that is why I write.'
Attributed. A report by Carl Czerny.
Quoted from Czerny, Carl: Erinnerungen aus meinem Leben: mit Werkverzeichnis (ca. 1860), ed. and annotated by Walter Kolneder, 1st edition, Baden-Baden: Verlag Valentin Koerner, 1968, p. 47. First published in Czerny's Anecdotes for 'Cock's Musical Miscellany' in English translation: 'On another occasion, the conversation turning upon the praise which his name had won in the world, 'Oh! nonsense,' he said, 'I never thought of writing for fame or honour. What is in my heart must come out, and that is why I write.'; cf. Czerny, Carl: Recollections of Beethoven, 1852, collection of anecdotes about Beethoven, first published in 'Cock's Musical Miscellany' (London). In a further contribution (No. 26, p. 204 f.), Czerny's authorship is questioned. In: Dwight's journal of music, 1 (1852), no. 24, 18 September, p. 186.

"Mein Fidelio ist vom Publicum nicht verstanden worden, aber ich weiss es, man wird ihn noch schätzen."
'My Fidelio has not been understood by the public, but I know that it will still be appreciated.'
Attributed to. Henry Hugo Pierson on Georg August von Griesinger's accounts of this alleged statement by Beethoven. 
Ludwig van Beethoven's Studien im Generalbass, Contrapunkt und in der Compositionslehre: mit Beethoven's Portrait und Facsimile nebst anderen artistischen Beilagen, aus dessen handschriftlichem Nachlassen gesammelt und ed. von Ignaz von Seyfried, second revised and textually completed edition, by Henry Hugo Pierson, (Edgar Mannsfeldt), Leipzig; Hamburg; New York, NY: Schuberth, 1853, Appendix, p. 24; cf. also TDR II, pp. 142-143; Kerst I, pp. 85-87; Nohl, Ludwig: Beethovens Leben, vol. 2: Das Mannesalter, 1793-1814, Leipzig: Ernst Julius Günther, 1867, p. 494