Often I think of that excellent painter Monticelli,... when I come back myself from the mental labor of balancing the six essential colors.... sheer work and calculation, with one's mind utterly on the stretch, like an actor on the stage in a difficult part, with a hundred things at once to think of in a single half-hour. Don't think that I would artificially keep up a feverish condition, but do understand that I am in the midst of a complicated calculation which results in quick succession in canvases quickly executed, but calculated long beforehand. So now, when anyone says that such and such is done too quickly, you can reply that they have looked at it too quickly.