It has taken me a while to figure this out, but here it goes. When writing a short story, I rely on my unconscious mind to write the story. In the editing process, I shape it into something more concrete, often editing it a dozen or more times. Every word goes under the scalpel.
You can't do this in a novel. You'd spend years writing it this way. Your unconscious is not going to come up with an entire novel. You can't edit a novel into existence.
So you have to either outline or have a pretty great memory. Thus far I haven't outlined my WIP, so I think it's still going to read too episodically. Does this happen to you and how do you deal with it? When you sit down, what percentage of what you're about to write is already in your conscious mind? How much of the time do you fly by the seat of your pants?