Guidance provided in self help books and in formal publications and methodologies should be interpreted in the context of the intended audience and the actual situation that you are in.
Some guidance are meant to be rules of engagement. If not followed it has a negative impact on the coordination within the team or organization that it was intended for. Definitions of terminology, and protocol, for instance.
In other areas, guidance is meant to be flexible. It says what might be expected in a given sphere of operations, or life, etc. But it cannot be all encompassing or strict in rules because the environment for which it is intended is always in a state of flux.
An example of the former, where rules and definitions are essential to be followed with few exceptions are in project management methods where an objective has to be achieved within a relatively short timeframe and with little scope for variation. This is akin to the army where the rank and file has to follow orders without question.
An example of the second type of guidance with a lot of flexibility within a framework is Portfolio or Programme Management. This is akin to an army’s strategic level, where for a given objective, the path the actions take will have to be constantly modified to fit actual circumstances. The strategy itself may also eventually have to be modified to fit the external or internal situation.
When adopting any guidance, you have to be aware of the type of guidance it is. What the author says it is and what it really is, in your own circumstances may also be different.