Here are some comments about the artistic process from illustrators or other artists that I think are particularly insightful:
Don't stop to admire a partly completed sketch.
--Robert Fawcett
On always doing your best work: The argument that "it won't be appreciated anyway" may be true, but in the end this attitude does infinitely more harm to the artist than to his client.
--Robert Fawcett
On being accused of making art like a madman: There is only one difference between a madman and me. I'm not mad
--Salvador Dali
What one has most to strive for is to do the work with a great amount of labor and study in such a way that it may appear, however much it was labored, to have been done almost quickly and almost without any labor, and very easily, although it was not.
--Michelangelo
I ain't yet worked out whether I like girls because I like curvy lines or if I like curvy lines because I like girls.
-- some artist on the internet whose name I forgot to write down
On when to put the finishing touches on an illustration: The longer the idea can be considered in the abstract, the better.
--Robert Fawcett
There are moments when art attains almost to the dignity of manual labor.
-- Oscar Wilde