*smiles* Interesting question...
I am propelled to write for various reasons, and my general emotional/mental state will dictate the shape my writing takes.
Sometimes writing is a powerful release... I will have a huge mess of stuff swirling about inside that I simply need to get out. In this case my writing is a form of processing, and becomes largely therapeutic in nature.
Other times I am in a mischievous mood.. and well.. no knowing what might happen then..
Or I simply want to create a world in which I have a sense of control, a place that I can build as a stage director brings into being a play.