The article explores how cognitive biases—such as anchoring, availability, confirmation, overconfidence, and framing—undermine clinical decision-making by leading to premature closure and misinterpretation of data, ultimately resulting in diagnostic errors. It explains that while intuitive (System 1) thinking is efficient, it is prone to these biases, whereas analytical (System 2) thinking, though slower, is essential for accurate diagnosis. Drawing on extensive patient safety research, the article presents a comprehensive discussion of how these biases interact and offers practical debiasing strategies, including structured reflection, diagnostic checklists, seeking second opinions, and implementing cognitive timeouts. These methods are proposed as vital tools for general practitioners and specialists to enhance diagnostic accuracy and improve patient outcomes.