Neville doesn't think about death. He doesn't think about the inevitability of it, the finality of it, the irreversibleness of death.

He doesn't think about how his grandmother looks at the picture of her husband with a seldom seen smile, doesn't think about how old his grandmother is getting, and he doesn't think about his parents lying forever still, forever distant, and how even though they're breathing, they really don't do much living any more.

He doesn't think about death when Harry comes back with Cedric's body or when Sirius falls through the curtain and Harry can't understand why he doesn’t get back up or even when he watches Harry watching Dumbledore's body go up in flames.

In fact, the only time he's ever thought about death is the last time he sees Harry Potter, and very clearly realizing, "He's going to die. He's going to die, and he's never going to come back."

The pain of this is so great that Neville cannot even tell him good-bye, and though he has been weeping he weeps still more when he hears Ginny starts screaming hours later. He weeps at losing something he never had and with jealousy for the one who did.