Several years ago a good friend of mine decided to write a novel. I was excited when she showed me the first few chapters, but quite quickly her progress began to slow. She was making major revisions as she wrote, changing characters and key plot elements along the way. After several rounds of major changes, she lost steam and her novel remains half-finished.
To avoid a similar fate, when I started writing I used a technique I call "write forward" to create my rough draft. The idea of "write forward" is simple to understand, but it can be hard to do: only add new words to the end of the manuscript, saving the process of revising until after the rough draft is finished.
There are several benefits to this technique. First, it gives me an incentive to do a little more planning up front, which keeps me from writing sections or chapters that are later discarded. Second, it helps me get to the finish line more quickly. Staying focused on the goal allows me to separate writing and editing tasks, which makes sense since they each require a very different mindset.
A completed rough draft is a motivational tool for me. Although a lot of hard work still remains, I find it easier to massage existing words than to write new ones. Once I've made the effort to write a rough draft, I also find myself wanting to honor that effort by creating the final product.