Too much

Iroh was a man of fortune, benevolent fortune – that was his biggest flaw: whenever the fickle spirit would turn against him, Iroh would mope, preventing him from recovering the initiative. This flaw manifested only occasionally in his life – when his wife and son, Alia and Lu Ten, perished, and Iroh lost – the siege at Ba Sing Se, his chance to get his crown… But then, there was Zuko. Iroh's nephew believed in him, and little by little, Iroh began to believe that Zuko might be the man Lu Ten was becoming before he died.

Iroh was wrong. Zuko was nothing like Lu Ten, though he tried to be that man as hard as he could. For a while, it seems to work, as Zuko literally broke himself to be happy for his uncle in that tea shop of theirs. But then the Avatar came back, and Iroh wanted Zuko to help the bald monk of his own volition. It was too much. Zuko's true nature snapped back with an unusual extent, and disaster followed suit, from which Iroh never truly recovered.

Iroh's story, put short, is a story of a man who trusted the spirit of his fortune just a little too much.