Psychology
I don't know much about the psychology involved while creating (pixel)
art, so please don't take this part too seriously or as hard science.
I took some time to think over how the process could work in our most
precious tool: the brain.
The brains steers our hand to create a part of an illustration. As soon
as we have drawn something, the brain analyses what we have just drawn.
Basically the result of this analysis could be either 'right' or 'wrong'.
If we are lucky, or have spent a lot of time sharpening our drawing
skills, our brain tells us, 'good, well done'. Our journey quickly ends
here. Though the most preferable situation, this is not always the most
interesting situation.

In case our brain decides to disapprove and ignore our ego, an
interesting situation appears!
We have to find out what it is that causes the brain to tell us things
aren't right. This sounds easy, but most of the time it isn't at all
easy.
It can be very difficult to find out what's exactly wrong, most of the
time it's more of a feeling.
the complete page is available in the commercial version of this tutorial.