Writing a book can be hard. But all you need to do is love your idea so much that you can't stop.
Find an idea you LOVE. An idea that you can't stop writing until the last word is finished. That's when you know you have a good idea, you make it fun. Fun for you writing it and for others reading it. You have to revise and add things, you have to delete stuff just to find more information, but most of all, YOU HAVE TO LOVE YOUR STORY. Love your story even with the bad mistakes and the editing, the plot that goes horribly wrong, or the revisions that change your mind about writing the story. That's when some people quit, but not authors. Not people who love their story. They bear through all of those hard edits, and their story is better. All you have to do is revise, edit, and love your story. Trust me. It will turn out a lot better than you expected if you do.