What was Odysseus's life lesson in book 20

I think Odysseus learns who are his loyal friends and who are not. Melanthius, for example,resumes his mockery of the beggar (Odysseus), but a new arrival, the cow-herd Philoetius, offers Odysseus a hand and is kind to him. He laments the loss of his old master, and Odysseus reassures him that his master will return soon. They all go into the great hall, where there is a feast underway. The suitors continue their abuse of the beggar, with Ctesippus throwing a cow’s hoof at him.