It is only by drawing often, drawing everything, drawing incessantly, that one fine day you discover to your surprise that you have rendered something in its true character... So much the better if it is painful for you to take even the first step, the more toilsome the work, the stronger you will emerge from it... I repeat, guard against facility.

In a letter to his son Lucien (1894); as quoted in Painting Outside the lines, Patterns of Creativity in Modern Art, David W. Galenson, Harvard University Press, 30 Jun 2009, p. 84