How do aeneas’s piety and sense of duty change as the poem unfolds?

From the very beginning of the poem, Aeneas is aware that he has to follow the course of his destiny - and not the destiny he has chosen, but the one that was chosen for him (we might even say: imposed upon him) by the gods. However, even though he knows this, he is utterly unhappy about it and finds it difficult to leave behind everything that is dear to him. He sincerely grieves for his love with Dido, whom he has to leave. But in time, he gets to understand that his cause is a really worthy one.

The most significant shift in his character's development happens in Book 6, when he meets his father Anchises in the underworld. Anchises unravels to his son the future of the empire that he is to build. That is the decisive moment, when Aeneas realizes that all his personal sacrifice isn't for nothing. Hitherto, he had had many doubts and second thoughts about this sacrifice. But from that moment on, he will invest all his mental strength in his leadership, and commit fully and enthusiastically to his grand mission.