[He hates talking about this, but to teach Sokka, to get him to understand, he has to say it.]

...My skills have been diminishing since I was returned from the dead.

[The lack of a full set of functioning lungs makes it difficult to be on top of his game, and he still isn't entirely certain that's his death penalty.]

It takes years to be a certified teacher of our style. I don't wish to lose the ability to teach you before you know how to teach.