Not all authors reaction this way, but most do, especially new authors.
Don't panic. It's not the end of the world. In fact, it may help you sell more books. Here's why:
- Some people are looking strictly for free content. They'll read any books they can download for free. They go to bit torrent search engines or sites that like books that have been pirated, and they get stuff that sounds good. They are extremely unlikely to buy a book if it's not available illegally. They'll just go read something else that's free.
- Some people buy books. They have an ecosystem that they love, whether that's Amazon, iTunes, Smashwords, or Kobo, and they buy content in that ecosystem. They're extremely unlikely to forego buying a book just because it happens to be available on a pirated content site somewhere.
- A tiny percentage of people, probably far less than 1%, do fall into the category of people who will download for free if they can, and buy otherwise. But this truly is minuscule.
What does this mean?
First: It means that pirated copies are of your book are not likely to cost you very many sales at all, because few, if any, of the people who download pirated copies would have bought it.
Second: If your book is good, you're likely to get additional word-of-mouth advertising from pirated copies. Just as with paid copies, a small percentage of readers, probably about 1%, will tell others what a good book you've written, either through face to face interactions, social media, or blog posts.
Third: If your book has been pirated, congratulations! Someone thought it was good enough to share. And many more people will now read it! (Surely you want people to read it, because if all you wanted was the money, there's easier ways to make money.) Rejoice and celebrate: people like your book and they're reading it, and that will drive sales.
Does this mean I want everyone to steal my book?
Definitely not. I'd like to have enough legitimate sales to support myself as a writer. But I'm pretty sure most people will buy it, and that's enough for me. Even though authors who have given their books away for free online (Cory Doctorow comes to mind) are making it as professional writers, so clearly the free availability of a book doesn't preclude making a living from writing.
I do have a request:
If you download pirated books, support your favorite authors by recommending their books: tell friends, post on Twitter and Facebook, and write blog posts about it. Words cost you nothing but mean everything to authors.