Make a detailed outline of your story.
Invent a system Zolaesque…but buy a file. On the first page of the file put down an outline of a novel of your times enormous in scale (don’t worry, it will contract by itself) and work on the plan for two months. Take the central point of the file as your big climax and follow your plan backward and forward from that for another three months. Then draw up something as complicated as a continuity from what you have and set yourself a schedule.