Okay, so… there’s a lot of fanworks, including mine, that present how Aang’s death affected his loved ones, right? Well… what about Aang himself? At some point he must’ve known, or at least felt that something’s wrong. That he’s getting weak. At some point he must’ve realized that he’s dying. Probably he was the first one out of the Gaang. Imagine him preparing to tell them. Even though some of them (Katara, Toph, Tenzin) would probably sense that something’s off about him - he still would have the talk with them. Because I can’t imagine him pretending he’s okay, lying to the people who love him, while he knows that he’s dying. What he always feared the most was loneliness - and there he is again, about to lose “everything he knew and everyone he loved”, about to leave to a different kind of world. I think that no matter how much in touch he was with the Spirit World, he still would be scared, he still wouldn’t want to die. He loved his family too much.