Steven Pressfield named resistance as that powerful force that prevents us from making art. It manifests itself in many forms including friends, alcohol and fear. I contend that fear is the biggest contributor to lack solid artistic production in your life.
You haven't written that book because you're afraid of the effort required, the ridicule of your peers and costs of failure.
Here's the thing: Somewhere along the way we've been told that art has to be a published book or a youtube video with a million hits. Sure it's nice when those things happen, but the reality is not doing art is far more detrimental to your health than making art that society deems unworthy. It's art because it pushes the boundaries and limits of you and your vision of the world.
When you overcome the resistance of fear, you'll soon see that banging away on your craft can fill a massive void in your self actualization.
Who cares if it's bad?