Writing is sometimes thought of as being the ultimately best job for an introvert. After all, the writer works in relative solitude, "just me and my story", even if sitting in crowded coffee shop with a latte (or at home with the chaos of kids and family life going on all around.) Every writer dreams of that moment when their book sits on a bookstore shelf and that one special person is drawn to take it from the shelf and open it up....
Well, sorry to burst a bubble, but the book has to get on that shelf somehow. I won't depress anyone with the exact number of new books that are published every year, or even with how that measures up to the amount of available shelf space at your local bookstore (whether it's a five-story Barnes and Noble flagship store or a small indie book seller.) Just writing a book and getting it published does not guarantee readers.
This is where promo work comes in and it is the bane of the existence of most writers. Few of us want to leave our little cocoon of anonymity. Yes, we want our name on the cover and for it to be recognized, but we'd just as soon be the faceless silhouette that is the default Facebook profile image. However, it doesn't work that way. We can't imagine ourselves standing onstage and singing or acting or dancing, so the idea of holding up our book and saying, "Look, I wrote this and it's a great story! You should read it!" gives us near-fatal stage fright.
I was probably the worst at selling Girl Scout cookies in our troop back in the '70s and God knows that Thin Mints sell themselves. Writing my books was nowhere near as difficult as mustering the courage to knock on a publisher's door and say, "Would you like to buy a mystery novel?" And once I did get published, I was having to walk up (literally) to a bookstore owner and say, "Will you carry my book in your store?" I learned very quickly that, as difficult as it was, that was probably the most important part of the job and I had to learn to do it. And even if I didn't enjoy doing it, I wasn't going to let on!
Selling a book means selling the author as well. A book is a reflection of the author (which is why we take rejection and criticism so much to heart) but it's important to remember that the author is a reflection of the book. An author who manages to convey excitement and interest in their work is an author who will find readers who want to know WHY this book is so worthy of the excitement and interest. Just as a parent delights in telling everyone, even total strangers, about their children and their accomplishments, an author should find joy in sharing their work with everyone... especially total strangers.
Writing IS the easy part!