Three quarters of all medical errors stem from cognitive error, rather than the systemic errors that most efforts address. This narrative/conceptual review posits that many clinicians are not fully aware of or sufficiently focused on the innate cognitive processes our brains use for clinical reasoning. References refer largely to standardized reviews or peer reviewed research: data that exceeds individual experience or opinion. Unsupervised, all humans revert to these ancient methods of estimation that were not selected for modern complex medical decision making. Clinicians must appreciate dual processing theory and the limitations of the various methods of clinical reasoning, in order to maximize our problem-solving skill and find ideal clinical outcomes. Our brains default inversely to more or less complex methods to process the amount of uncertainty they confront. We can utilize the most effective method, abductive reasoning, only by gathering as much data as possible, thereby reducing uncertainty to its lowest levels. Even expert clinicians not giving sufficient attention to reflection and feedback ultimately reinforce their error-laden processes. Overconfidence, intuition, reasoning across scales, and our innate preference for mechanistic explanations over clear outcome data add to cognitive error and diminished outcomes. We must strive to identify our method of reasoning at all times, form new clinical questions to fill information gaps, and utilize impasses as new sources of data to remodel our diagnoses and treatment plans, while developing and adding to our clinical and communication skills. Humbly seeking multilevel feedback, and learning from review of our own work are essential. Only by anticipating, recognizing, and countering these very human errors can we reduce treatment failure and suboptimal outcomes, and increase professional satisfaction.