That's cute, but this isn't Air Temple pre-school. It's the real world.
It wasn't until they arrived at the beach house and Katara brought it up that Zuko remembered even saying that, and now that he did, he felt like a world-class jackass. "You don't know how traumatic the loss of his people was for him, how hard it is being the last of his kind," she'd said.
Aang hadn't said anything about it or even twitched. If he'd had cried, scowled at him, told him off he would've felt bad, but not this bad.
Deciding he wasn't going to get any sleep tonight, he rolled out of his bed, slipped out the open window and pulled himself up onto the roof with a low grunt.
"Why am I so bad at being good?!"
"Zuko?"
Great. Why couldn't Aang be a heavy sleeper like Sokka or Toph? He heard the soft thump of the Airbender's feet as he landed atop the roof.
"What are you doing up here at this hour?" Aang asked as he sat down. Reluctantly, Zuko turned to face him.
"Aang, look...remember when we were fighting about Katara and what she needed? I...I owe you an apology."
"No, you don't." Aang shook his head. "It doesn't matter, it was three days ago and it's over. And you were right, anyway."
"Yes it does." Zuko bit his lip. "This isn't even about who was right, this is about me hurting someone I care about! Aang, I mocked your culture and tried to make you look stupid and naive, and I won't feel better about it until you get angry at me, so get angry!" he cried. "Come on, just-hit me or something!"
"Zuko, stop!" Aang's eyes were sharp, looking deeply into his. "Just stop...I forgive you, even if it was a mean thing for you to say I still forgive you."
"How can you?"
"Because you're my friend," Aang said softly, throwing his arms around Zuko. "That's how."
Zuko smiled, tears filling his eyes as he returned the embrace. It was the pure simplicity of the statement that touched him; they were friends, and that was all the reason Aang needed to forgive him. All the reason he'd ever need.
"Thank you," he whispered.