When my mother asked me about my sales the other day, I said that it is a slow summer but things will pick up "with the next book." I realized as I spoke that the answer came to me genetically.
My grandfather (her father) was an author, and at times a commercially successful one. He never quite rose to the fame of his friends (e.g. Kurt Vonnegut), and his work is not read often today, but he is survived by Wikipedia and IMDB pages. He supplemented his royalties with a long career of university teaching positions, or perhaps the income from the former supplemented the latter.
To his credit, my grandfather was a sufficiently industrious writer as to be described as "prolific" in a Washington Post Obituary. He published a couple of dozen times over his career, often enough that there was always another advance around the corner.
Indeed, "the next book" became an answer to many financial problems, and eventually other problems as well.
I didn't know my grandfather well; I only met him once or twice in my life. But I am very clearly his grandson. I have some of his best traits. Some of his worst ones. We'll see which type of trait faith in "the next book" turns out to be.