"According to Nahua cosmology humans came upon the earth, created by the gods after several attempts. These humans needed to respect the gods by performing ritual ceremonies designed to move time forward and thus allow for the continued survival of the deities. These humans had bodies made up of a variety of substances that could be exchanged at particular (ritually important) moments. Moreover, the human body always maintained a very close connection to both the natural world and the world of the gods. Hence a Nahua could not view the human body in isolation from the existence of the gods or from the centrality of plants, animals, and the earth. And humans could also alter their bodies, though only in ritually appropriate ways, and only with the support of the gods."
Still from the first few pages, this quotation oddly seems much more in line with other interpretations I have read -- primarily those of Miguel Léon-Portilla, who it would seem might be closer to the Nahua cultural strand than Pete Sigal -- than later in the book, where Pete presents a much more Freudian interpretation of Nahua ceremony, ritual, and (especially) sacrifice. He describes these things later in the book not as moving time forward (which would vibe with Miguel's interpretations of the centrality of ollin/motion and seemingly the etymological connections between teyolia/lifeforce, yollotl/heart, and ollin), but as renewal of fertility by engaging with necessary-but-dangerous excess and also as Freudian castration play, gender inversion, and the power of being "penetrated" (even if by a tecpatl/knife rather than a tepolli/penis). It's very confusing.
But this one paragraph does seem like a nice little summation about the role of humans in the Nahua cosmology; I don't recall Miguel ever providing anything so succinctly broad, so I will be using this until I can find something better . . .