Drawn & Quarterly recently linked to this Seth sketchbook comic and essay by cartoonist Seth as well as a web-only interview, both from Canadian mag The Walrus.
In both pieces there are some choice quotes about the cartooning process:
…when I am drawing or inking I am often running a kind of low level tutorial in my head, as if I was talking to a student, explaining why I am making each move of the brush. Why I am fixing up this line and why I am taking out that one.
There is no point in doing the work if it is going to be watered down.
I always tell aspiring artists that if they want to be cartoonists, they’d better enjoy being by themselves.