Best parts - the big structure (psych, prep, perspire, persist, persevere) and the timeline - the idea of step mismatching. Certain tasks (like deciding if a change is worth it) are helpful at some stages but not others (in this case, psych but not persist) - the emphasis on tracking progress and when, where, why, and with whom you slip - the idea of having a slip recovery plan, i.e., thinking in advance about what to do when you fail (e.g., remember a slip is not a relapse and call a friend)
Worst parts - the author holds the unbiblical view that humans can change anything about themselves on their own. So, he sees God as unnecessary and is critical of Jesus and some Christian ideas. - the author’s explanation of motivation is shallow. When deciding if you should change something, he says simply count the positives and negatives. If more positives, do it. If more negatives, don’t. This is somewhat good but simplistic. There is no mention of certain reasons having more or less weight.