In the end, keep writing
So, you’ve published a book, done some good marketing, and you’re feeling good about yourself and your future as a writer. What now? Write another book. It will probably be better than your first one. Go to some conferences and learn how to be a better writer. Write some more.
Writing, unfortunately, isn’t like riding a bike. If you aren’t constantly honing your craft and striving to become better, your skill will diminish and your ability stagnate. Writing is a tool of self-expression and – like any tool – if you don’t give it the proper care and maintenance, it won’t perform adequately when you need it to.
Hopefully, you never stopped writing. Even when pitching your novel, even when editing something else, you should be be thinking of new story ideas, new ways of expressing characterization, and how to better improve yourself and your craft. That’s the real key to being a writer. Be a writer. It’s not something you can turn on and off. Be it. Live it. Breathe it. Consistency is the key. Keep writing.
Consistent improved practice makes perfect.
Keep at it. You can do it. You will.