In book writing (I have written almost a score of books), the length of time between start and finish can be prolonged agony, requiring that the writer respond daily, weekly, monthly, even over years, to get it done right, often without any assurance of acceptance. Example: I spent 8,000 hours over an eight-year period researching, writing, editing and fact-checking a fact-based novel that was not, eventually, published (scratch four years’ worth of professional work).
Most people don’t understand these challenges. But they are no different from the challenges in every profession of which outsiders are unaware. It is fair to assume that success in any field is difficult and that the devil is in the details—details that are often invisible to observers.
Source, Quora: What aspects of a writer’s life are most people unaware of?