Resisting the Urge

I'm plugging away at my first draft and am resisting the urge to go back to the beginning and adding more. I know that I need to flesh out the start of the book more, but I also know that revisions are best left for after the first draft is finished. It is one of the hardest things for me. I'm doing nicely and staying on goal for this week. We are well into the muddle of the book. Muddle is correct. It's the way to get from point A to point B through Points X,Y and Z. I'm working on character development and the next section will add a bit more of an action element. If the characters will oblige.