Writing and publishing a book does not result in immediate sales. If you are an independent writer, you know that. For most writers, the treasure chest doesn’t open wide enough, and if the only motive is to make a significant amount of money, a dose of reality can knock down your pen. Expectations and motive when writing and publishing a book will determine the level of discouragement when sales do not materialize soon enough. The definition of success will also correlate to those two. Do you consider a success writing and publishing the book (s) or will a lack of sales point towards failure? Again, motive and expectations will determine how a writer views his/her success or failure at the craft, and how this will influence future works.
For many writers, absence of sales is enough to discourage them, hence why many never publish again. Money or recognition was a strong motivator, maybe the only one. In the absence of it, writing does not make sense anymore because it is not profitable. Other writers view the craft as a venue to tell a story, to inspire others, and even as an outlet for their mental and emotional health and enjoyment. For this group, money becomes secondary and not a goal. These are the writers that have been writing for many years and keep at it, even when monetary rewards elude them. Their passion for writing supercedes any monetary value or desire for fame and recognition.
In a now very saturated market, those who remain have realized and understood a bigger why, and in the process defined their own success. In that sense, book sales become a sickle and a passion builder.