Your work is going to fill a large part of your life and the only way to be truly satisfied is to do what you believe is great work. And the only way to do great work is to love what you do. If you haven't found it yet keep looking. Don't settle. As with all matters of the heart you'll know when you find it.
The act of writing... is the act of trying to understand why my opinion is what it is. And ultimately I think that's the same experience the reader has when they pick up one of my books.