You didn't think at all, Blockhead. Listen, if Zuko broke it off with Katara, that'd just make everything worse. Aang'd feel bad for causing them to separate, Zuko'd be miserable because Aang's upset and he's not with Katara, and Katara'd be upset because that'd be at least the second guy who ended up hurting her. Maybe third, the jury's still out on Haru. I know my friends a lot better than people give me credit for, trust me here.