While Aang was trying to strengthen his bonds, Zuko was busy breaking them.
His mind had been made up. He wasn't happy in his home, despite having more wealth and love and respect than he could've hoped for. The world around him was suffering at his family's hands, and he couldn't sit back and watch anymore – he wasn't happy keeping quiet and acting like the perfect son. Guilt over his uncle's poor treatment weighed heavy in his mind. Katara's aura, intertwined carefully with his own, was like lead.
Yue encouraged him. This, after all, was the right thing to do (and his destiny, according to the Stars). Plus, the sooner he moved away from Mai and closer to Katara, the sooner she could do her job and push them together.
Writing a letter instead of confronting Mai was Yue's idea. Granted, Zuko had already been considering the temptingly easy option (compared to looking her in the eye when he dumped her? Definitely a more desirable action), and all she had to do was give him a little nudge.
The words he wrote were all his, though. She had read over it, and instantly knew Mai would not be pleased.
While certainly meaning well, Zuko had no tact when it came to breaking up with a girl.
Author's Notes: Ditto the last chapter. Though, I do enjoy writing about Zuko being socially incompetent. xD
Disclaimer: I do not own 'Avatar' or any of its characters.