He was the Avatar, the destined hero, the only one who could restore balance to the world and end the Fire Lord's reign of terror. Everywhere they went he was reminded of it, hell, even Aang himself wasn't against introducing himself as the Avatar if he had to (though he hated to flash it like a calling card).
But at the end of the day, he was still just a kid, Zuko thought somewhat bitterly as he watched Aang sleep. Zuko remembered his childhood with regret and anguish, but had Aang ever even had a childhood?
He smiled a little. Aang was a good kid, a little naive and idealistic, but someone had to be at times like this.
When we finally defeat my father we won't need to restore balance to the world ever again because the world is gonna stay balanced forever.