Sells go up and go down and that's simply the Universal Law of how business and our existence works ... there are seasons.
This is a reminder that while you may experience dips to stay focused, follow your system, continue to research, upload, test and tweak as necessary and over the long run you should experience residual/passive revenue.
With that being said, as it's been mentioned more than once, don't let Kindle be your only source of revenue. It's up to you to find various ways to tweak the system to create new opportunities. Some of the things I've been doing include offline ebook publishing coaching/consulting, working on turning some of my best sellers into physical and audio books, selling affiliate products and so forth.
I look forward to reading your comments about how you're making Kindle publishing work for you.
"THINK, PLAN, EXECUTE!" -JAWAR