The pen works for itself …

Henry Adams in his study (source)

The pen works for itself, and acts like a hand, modelling the plastic material over and over again to the form that suits it best. The form is never arbitrary, but is a sort of growth like crystallization, as any artist knows too well; for often the pencil or pen runs into side-paths and shapelessness, loses its relations, stops or is bogged. Then it has to return on its trail, and recover, if it can, its line of force. The result of a year’s work depends more on what is struck out than on what is left in; on the sequence of the main lines of thought, than on their play or variety.

Henry Adams (1838–1918), American historian and journalist, writing in “The Dynamo and the Virgin,” chapter 25 in his autobiography The Education of Henry Adams.