I interpret it as "Don't fall in love with your writing."
Last time I wrote fanfic, I spent considerable time thinking about world building, the backgrounds and personalities of secondary characters and interesting scenes.
Very little of this made it into the finished fanfic, because it was irrelevent to the story, boring info dumps or would have taken focus away from the central story.
You have to be objective about your writing and willing to prune harshly.
Last time I wrote fanfic, I spent considerable time thinking about world building, the backgrounds and personalities of secondary characters and interesting scenes.
Very little of this made it into the finished fanfic, because it was irrelevent to the story, boring info dumps or would have taken focus away from the central story.
You have to be objective about your writing and willing to prune harshly.