Shorts to Novels; Belief in the Creative Flow

As I approach the halfway mark in my Novel I've started to become a little more relaxed and positive about trusting the 'Creative Flow'. This Novel has been in development from the very first conceptual process to actually putting every bit of planning into writing it for at least 14 months. During those 14 months character profiles, brief timelines, back-stories have been changed quite dramatically, and as I've been writing it I've found myself concentrating TOO hard in order to make sure all the planning is executed correctly. Yes, there is such a thing as concentrating TOO hard, of course there is. With my writing I've been guilty of doing it before, but sometimes you have the idea and you plan it then when it comes to writing you get sucked into this worry that it wont be good enough, or that the genre wont be right, or that this wont go right so you try to mould it as much as possible. That cut's out the belief in 'creative flow'. When I say Creative Flow what I mean is the self-belief that you've thought of a good story and will thus write a good story. You have to give yourself the freedom to then go ahead and write it, write it being aware of what you're writing... but to an extent. There's no way that any writer will allow himself to write a poem/short story/epic/saga/novel without reading through it and editing about a million times. So the way I look at it is that you should write it, change things if you feel they desperately need it or they don't work with other bits, but ultimately trust yourself to finish it first, and then go back read it and edit it with a fine tooth comb. Writing is a fun thing to do, if you go through the whole process worrying and be over-critical before you've finished then you're completely changing the happiness and wonder of the process.