Every human being has a life management system
Whether consciously or unconsciously, every human being is already living according to a rough understanding of the natural world (theory) and reasons for acting a certain way.
All of us are living lives within a framework that can even be understood by outside observers. This framework is already a life management system. It is the product of our mind's ability to identify patterns in the natural world and in our own behaviors.
Wether we're aware of it or not we live according to our theory of the world and a structure we unconsciously build around that theory. Part of intentional living is being conscious of these structures, being able to articulate them, and add necessary layers on top of them so that one can manage one's actions (and, therefore, life) better.