Per former Hollywood Development Executive Dan Watanabe, one of the biggest ways writers fall short with their stories is that they don't write the story they are meant to write. Many writers are too worried about what's trending in the book market. He recommends writing from your gut and finding the element within that story that is marketable. It may not be obvious right away, but you will figure it out.
Watanabe also believes it's critical to get feedback on your writing before you begin pitching it or trying to get it published. You need to understand what's working well in your story and what readers enjoy. If you focus on your weaknesses you will get blocked. In addition, Watanabe cautions writers not to get hung up on their writing process. What works well for other writers may not work well for you. Maybe you need to write your story out of order, or outline after the first draft to make sure the plot works. There is no right or wrong way, he says, you just need to get it done.