Decisions that Fit: How Self-Knowledge Shapes Better Choices offers a practical, research-based approach to one of life's most essential skills: making sound choices. I present decision-making as a learnable discipline that depends on three key resources: personality, knowledge, and skills. The book guides readers through the psychological foundations of choice, examining how cognitive biases, emotional states, and personal values shape every decision we make—often without our awareness. Beginning with fundamental concepts, I distinguish decision-making from critical thinking and explore why intelligent people frequently make poor choices. Readers learn how mental shortcuts (heuristics) can both help and hinder judgment. The heart of the book provides an extensive toolkit for better decisions: analytical frameworks such as SWOT analysis and decision matrices alongside strategic concepts like scenario planning, no-regret actions, and the stop-loss principle. I draw on sources ranging from Stoic philosophy and Chinese stratagems to modern therapeutic approaches like Acceptance and Commitment Therapy (ACT). Practical exercises form a substantial portion of the work. Six-week training plans address decision-making under stress and during anger. Journaling templates, reflection exercises, and role-based planning methods help readers apply concepts immediately. Special attention is given to personality traits (the Big Five) and how individuals with different tendencies can optimize their decision-making processes. The book concludes with advanced concepts including design thinking, the consulting approach, and naturalistic decision-making. A historical appendix traces the evolution of decision-making practices from ancient philosophy through the age of artificial intelligence. Written for anyone seeking to improve their choices—professionals, leaders, students, or anyone facing important life decisions—this book combines intellectual depth with actionable guidance. My goal is simple yet profound: to help readers make fewer wrong decisions and live a life that is truly their own.