Editing, editing, editing.  Sometimes the writing of a book seems like the easiest part of all. And the editing, querying, selling, and marketing can feel like a lonely process. 
No one really understands or can really sympathize with the feelings and emotions tumbling around inside you. Of course they say they do, but only another writer can really understand the delayed hope and half-buried dreams that a writer keeps inside. 
Writing is fun and exciting, but with it comes the ups and downs of fame and fortune, and a lot of lonely hours by yourself, dreaming your dreams and drinking a lot of coffee.