Part of your work feels as clear, it gives you a sense of liberation or beauty and you recognize it as necessary pavements. You are thus in a sense ready. In the other part of your work this is not the case. Therein is the hidden development, which is the true essence of art... the higher purpose, the pursuit forward that art automatically calls. The unclear part of your work needs to progress (stopping is no option, is no life, no art) and it is clear when by working with head and heart, the real step forward has been achieved.
Letter to B. Kramers, 1926, as quoted in: Bram van Velde, A Tribute, Municipal Museum De Lakenhal Leiden, Municipal Museum Schiedam, Museum de Wieger, Deurne 1994, p. 18 (English translation: Charlotte Burgmans)