Why does the author end up breaking the rules she set for herself?

Ehrenreich details the parameters she set for her endeavor. First off, three rules: she was not allowed to fall back on skills derived from her usual work; she must take the highest-paying job offered to her and do her best to hold it; she must accept the cheapest housing she could find. The problem is that she wound up, by her own admission, breaking all three of these rules in one way or another. Sometimes she simply could not starve herself. At other times her safety was in danger.