The narrator says that variety is what keeps him from getting bored as he continues through the long journey of the story he’s telling. He once again asks his Muse for guidance as he continues on this journey. He notes that out of all the virtues, which grow like flowers, perhaps none of them bloom as beautifully as courtesy. True courtesy, which is different from false imitations of courtesy, is valuable and embedded deep in the mind, but the narrator hopes to show how his queen embodies this virtue.
Courtesy is an important virtue not just in Book VI of the poem but in many prior books as well. While politeness is an important part of courtesy, the virtue is bigger than simple politeness. It signifies good behavior and adherence to chivalry on a wider level, and that makes it one of the most important qualities a knight can have.