Question

“Scout,” said Atticus, “when summer comes you’ll have to keep your head about far worse things… it’s not fair for you and Jem, I know that, but sometimes we have to make the best of things, and the way we conduct ourselves when the chips are down—well, all I can say is, when you and Jem are grown, maybe you’ll look back on this with some compassion and some feeling that I didn’t let you down.

How does the author use this element to construct theme?