This book explores how the conceptual lens of Holistic Flexibility presents new advancements in systems thinking. Systems thinking is often associated with frameworks and methodologies that often confine the discipline to academic circles in operations research and management science (OR/MS). Holistic Flexibility for Systems Thinking and Practice challenges this status-quo and talks about systems thinking as a state of mind, giving it a cognitive character. The book presents both theoretical deliberations and practitioner cases of Holistic Flexibility. The development of systems thinking in OR/MS is described leading to the latest debates on the subject and the key pillars of Holistic Flexibility are discussed in detail. A range of case studies are presented that offer a firsthand experience of Holistic Flexibility in practice. Learnings are drawn to highlight the importance of a spiritual approach in management, an understanding which is used to further develop the conceptual lens of Holistic Flexibility since it was first introduced. This book presents a range of competencies required for systems practitioners to address and respond to complex situations in an interconnected world. A bold attempt to pragmatize systems thinking and systems practice, the ideas presented in this book weave a thread between the development of the discipline, current debates, and what lies ahead. It will be highly beneficial for OR/MS researchers and graduate students who are interested in systems thinking as well as researchers interested in connecting modern management thinking and Eastern mysticism.