Adams claims that "Science has demonstrated that humans have a limited supply of willpower." This idea is important for at least this chapter. However as Robert Kurzban has noted it is a weak theory that cannot be falsified.

We know that humans act roughly as if they have a limited supply of willpower. That is, it is a reasonably functional model for predicting a variety of experimental outcomes. As a rule of thumb for purposes of providing self-help advice that applies in most cases, this seems pretty sufficient.

I would prefer Adams to use the concept of willpower as another self-delusion to help optimize one's systems.

IIRC, I think this falls under his general admonition not to treat the contents of the book as true, but rather as useful.