Writing, like any art, is creative exploration. In my own case, that works best if I follow my inspiration. I probably finished, or came close to finishing, the first draft of my latest novel half a dozen times. When inspiration comes, don’t turn away from it. If it suggests you write, write! If it suggests you edit, edit! It may also suggest you kill out your favorite characters, lose your favorite scenes, or re-distribute whole chapters. It may not be what you had planned, but if you keep pushing forward you will likely be much more excited by whatever you and your muses write together than you would have been by following only your own original plans and concepts.