One of my favorite comix artists, Seth, wrote an essay for The Walrus about "the quiet art of cartooning." It's a lovely piece and gives some nice insight the artist's mind at work. Seth's article is accompanied by a comic strip and also an interview with him. From The Walrus:
A cartoonist isn't like a writer. Writing requires a special kind of focus. Your mind must be utterly devoted to the task at hand. When I'm breaking down a strip or hammering out dialogue, I'm using that writer's focus. But drawing and inking are different. They use different parts of the brain. I often find that when I'm drawing, only half my mind is on the work – watching proportions, balancing compositions, eliminating unnecessary details.
The other half is free to wander. Usually, it's off in a reverie, visiting the past, picking over old hurts, or recalling that sense of being somewhere specific – at a lake during childhood, or in a nightclub years ago. These reveries are extremely important to the work, and they often find their way into whatever strip I'm working on at the time. Sometimes I wander off so far I surprise myself and laugh out loud. Once or twice, I've become so sad that I actually broke down and cried right there at the drawing table. So I tell those young artists that if they want to be cartoonists, the most important relationship they are going to have in their lives is with themselves.