A couple of favorite Edvard Munch quotes from his journals:

There should be no more paintings of interiors and people reading and women knitting. There should be images of living people who breathe and feel and suffer and love — I shall paint a number of such pictures — people will understand the holiness of it, and they will take off their hats as if they were in a church.

I stagger about amidst life that is alive. 

Just as Leonardo da Vinci studied the recesses of the human body and dissected cadavers, I try to dissect souls. 

. . .

In a strongly emotional state of mind, a landscape will have a particular effect on one. By portraying this landscape, one will produce a painting which is affected by one’s own mood. This mood is the main thing. Nature is simply the means.
     Whether or not the painting looks like that landscape is beside the point. Explaining a picture is impossible. The very reason it has been painted is because it cannot be explained in any other way. One can simply give a slightly inkling of the direction one has been working towards.
I do not believe in any other art than that which is forced out by the human need to open one’s heart.
All art – literature as well as music – must be generated from the blood of one’s heart.
Art is one’s heart blood.

For more excerpts from Munch’s journals, and some reflections on them, visit here.