I've been reading a lot of interpretations of Achilles' decision to return to battle, and many top scholars seem to think that he sacrificed his life in order to achieve some form of eternal glory. For example, both Gregory Nagy and Bernard Knox (Harvard Center for Hellenic Studies) saw Achilles' decision to return to battle and sacrifice his life as the ultimate choice of eternal glory/fame (see my article on the subject for more information).
But it seems like his own words and actions suggest otherwise. For example, When Achilles leaves the battlefield after his dispute with Agamemnon, the Trojans gain the upper hand on the Greeks. Desperate to convince their best warrior to return, Agamemnon sends an envoy of Achilles' closest friends to his tent to persuade him to reconsider his decision. During this scene, Achilles calmly informs his friends that he is no longer interested in giving up his life for the sake of heroic ideals. His exact words are below:
The same honor waits for the coward and the brave. They both go down to Death, the fighter who shirks, the one who works to exhaustion (IX 386-388).
I wrote an article that into more depth on this question but I'm still confused. The most straight-forward explanation seems to be that Achilles returns to battle solely out of rage and the desire for revenge. Am I missing something?