How we cite our quotes:
When gods are contrary
They stand by no one. (2.532-533)
Another way of stating this sentiment would be, "When it rains, it pours." Like all of classical literature, the Aeneid presents a highly nuanced view of the gods. Even though they're sometimes on your side (especially if you honor them with sacrifices and prayers), if they turn against you, it can be deadly. The destruction of Troy – the context of these lines – definitely falls into the second category.
'Another thing: when you have crossed and moored
Your ships ashore, there to put up your altars
For offerings, veil your head in a red robe
Against intrusions on your holy fires,
Omen-unsettling sights amid your prayers.
You and your company retain this ritual
Veiling in the future, let your progeny
Hold to religious purity thereby.' (3.545-552)
When performing a sacrifice, it was very important to make sure you got all the details of the ritual right – otherwise you might mess up the whole thing. As a rule of thumb, whenever you hear a character in the Aeneid talk about how a tradition that happens "now" (i.e., in the world of the Aeneid) will continue to happen in the "future," there's a good chance that it might refer to something in the present in which Virgil is writing. In this case, Helenus is probably referring to the return of old-time religion that Augustus brought about, in order to distract people from his radical political reforms. Heck, in this statue the guy even had himself depicted veiling his head while making a sacrifice – just like Helenus says.
"Poor fellow, how
Could rashness take you this way? Don't you feel
A force now more than mortal is against you
And heaven's will has changed? We'll bow to that!" (5.602-605)
Were we suggesting that Augustus might have been using religion as a pretext? We were. But hey, it isn't only real people who can do it – quasi-fictional characters like Aeneas can, too! In this case, Aeneas is invoking the gods to break up the boxing match between Entellus and Dares, saying that Entellus clearly has a divinity helping him. The only problem is, Virgil hasn't told us about any gods getting involved, so it's a safe bet Aeneas didn't see one either. So long as the gods often act invisibly, the chances are high that someone will claim they've been acting one way or the other when the moment calls for it.