It’s important to find joy in your work. My work suffers greatly when I’m not enjoying myself. And really, what’s the point otherwise?
This phenomenon of joy also serves to indicate how important it is to know your interest in an idea will last the life of a project. You don’t want to get through half a novel and realize you’ve grown bored. It’s best to allow an idea to gestate. The best ones keep coming back to mind and expanding, while the muck gets sifted out.