Here's the deal--you're thinking about a very time-consuming project and you're going to be making course corrections and project-changing decisions along the way, which no amount of planning can anticipate. The journey is the destination times a hundred. You gotta jump in. No big buts.
Make a schedule and a goal stick to it. A page a day, a half-hour a day, every morning before work, whatever. This is your new part-time job. No buts at all.