I read "Start Small, Stay Small" back in 2011 and it helped me set realistic expectations. It helped me create a long term vision for my product with the expectation that it may always just be a side project and that was okay. I've been running it for 11 years now and while it's not a full-time job, it's a nice sustainable side business that keeps chugging along even if I have to ignore it from time to time.