All Marines are expected to invest effort towards increasing their:

The principle that all Marines should focus on personal development aligns with the broader goals of leadership and growth within the Marine Corps. Personal development encompasses a wide range of areas, including mental, emotional, and professional growth, all of which contribute to a Marine's overall effectiveness and capability as a leader. This holistic approach not only enhances the individual capabilities of Marines but also strengthens unit cohesion and readiness, ultimately benefiting the entire Corps.

Investing in personal development means continuously seeking to enhance skills, knowledge, and competencies, which are essential for adapting to the demanding and evolving nature of military service. This commitment can manifest through education, training, self-reflection, and mentorship, fostering an environment where Marines can thrive both inside and outside of their military obligations.

While combat skills and physical fitness are undoubtedly crucial elements of a Marine's responsibilities, they fall under the broader umbrella of personal development. Focusing solely on combat skills or physical fitness may overlook the significance of intellectual and emotional growth, which are vital for effective leadership. Personal wealth does not align with the core values and mission of the Marine Corps, as the organization emphasizes service and sacrifice over financial gain.