Self-esteem forms a critical component of mental health, as an absence of self-esteem is associated with mental disorders like depression. As such, understanding the nature and meaning of self-esteem and related phenomena like self-perception is essential for treatment of a variety of mental illnesses. Chapter One utilizes terror management theory to explain what self-esteem is, how the need for self-esteem develops, how people attain and maintain self-esteem, and why self-esteem is so important for psychological well-being. Chapter Two demonstrates how self-esteem is the fundamental mental attitude that provides the qualities necessary to perform democracy and reject authoritarian threats. Chapter Three deals with the definition of self-awareness, the description of the neural substrates that have been associated with it, and the examination of an interpretive neuroanatomical model of the phenomenon, with a focus on neurological and neuropsychological diseases. Chapter Four advocates a culture of self-evaluation as part of academic and professional culture through critical reflection on teaching and the results of one's own work. Chapter Five analyzes self-concept as a predictor of the academic self-efficacy perceived by adolescents. Lastly, Chapter Six studies the relationship between testosterone levels and self-esteem in school-age boys and girls.