How do you stay motivated when your book barely sells in the first months?

That stretch is normal and almost nobody talks about it honestly. A couple of things helped me. First, stop watching the sales dashboard daily — it's noise at low volume and it only feeds the anxiety. Check it weekly at most. Second, move your sense of progress off sales and onto things you control: words written, reviews earned, list subscribers, a new retailer added. Those compound; a single book's early sales usually don't. Third, the strongest marketing you have is your next book, so the best cure for a slow launch is often to be writing the follow-up rather than endlessly tweaking ads on the current one. It genuinely does get easier once you have a small backlist working for you.