He was sent on a mission before his first death. He was sent on a mission to do something, and it’s like, that’s what he’s clinging to. He’s forgetting other things, he’s forgetting who he is, or where he lived. He’s forgotten the woman who he was once supposed to marry. Bits of his humanity are lost every time he comes back from death; he remembers that mission. His flesh is falling away from him, but this one thing, this purpose that he had is part of what’s animating him and bringing him back to death.
George R.R. Martin
Melisandre (The Red Woman) resuscita John Snow: