Despite significant advances in strategic management, behavioral strategy, and organizational decisionmaking, organizations repeatedly fail to recognize, frame, and respond effectively to major strategic disruptions. This persistent pattern suggests that strategic failure is not primarily a problem of information, resources, or execution, but rather a failure of strategic diagnosis. This paper introduces Strategic Management Psychology (SMP) as a distinct conceptual and diagnostic field focused on the psychological substrates of strategic blindness, diagnostic incompetence, and organizational inertia. SMP examines how senior decision-makers perceive, interpret, and classify strategic phenomena, and how these cognitive and psychological processes systematically shape strategic responses. Using the contemporary case of generative artificial intelligence (GenAI) as an illustrative context, the paper demonstrates how misdiagnosis at the cognitive and governance levels leads to predictable and recurring strategic errors. The study positions SMP as complementary to, yet conceptually distinct from, behavioral strategy and organizational psychology, offering a structured diagnostic lens for analyzing strategic decision-making failures in complex and uncertain environments.