Watched it about a week ago, I think there really wasn't much that could be told about Nathan's life because when you have a condition like that, your whole life really just becomes about it.
Essentially, you're stuck with pretty basic routines. I say this because you expected more on that end.
Notwithstanding, I believe the only thing I hated about the movie was that Sherry was in on the robbery, otherwise it was entertaining, which pretty much is all I expect a movie to be.
A message I believe was subtly passed across, at least to me was the consequence of not feeling pain.
People usually will talk about wishing they couldn't feel pain but this movie reveals that such disability only increases your chances of dying sooner.
Pain are signals our body sends to let us know all isn't well somewhere, without that, well, night night we go.