A Theory is a description of some aspect of the natural world. If a theory describes the natural world, then it describes something that is objective and absolute.
A Philosophy of Living, on the other hand, incorporates this objective and absolute description of a theory into a bigger worldview to answer the question how should I live or how to live It needs to answer “why” we act a certain way. For it to extrapolate on why we act the way we act, it needs answers about what constitutes an action or a world where action is possible. These are answers that can only be provided by a description of the natural world, which theories provide.
Lastly, a system is simply a generic term that means a whole with interrelated parts. A life management system is one such whole and its parts work together to assist a human being to manage his actions (a life management system should free your mind; build a life management system that helps you take intentional action).
The management of one’s actions is only possible through an understanding of a theory about the natural world and a philosophy of living. These are, therefore, parts of a life system, which are arguably also systems of their own. Along with other systems, theory and philosophy of living create this beautiful array of a life system.