It is commonly said that men are forward to believe whatever is connected with their own interest. This in common cases is true; but it is also true, that when some very great and unexpected good news is brought to us, we find it very difficult to credit it.
At first, I see pictures of a story in my mind. Then creating the story comes from asking questions of myself. I guess you might call it the 'what if - what then' approach to writing and illustration.