Whether you think you can, or you think you can't — you're right.Henry Ford — as attributed
Self-efficacy is the belief in one's own capacity to execute the specific behaviors required to produce specific outcomes. It is not general confidence or self-esteem. It is the task-specific conviction that you can do this particular thing in these particular circumstances — and psychologist Albert Bandura, who identified and named the concept in the 1970s, found it to be one of the most powerful predictors of human behavior across every domain he studied.
The distinction from self-esteem is important. Self-esteem is a global evaluation of one's worth. Self-efficacy is a specific prediction about one's ability to perform a specific task. A person can have high self-esteem and low self-efficacy in particular domains, or low self-esteem and high self-efficacy in their area of competence. It is self-efficacy, not self-esteem, that predicts whether a person will attempt difficult tasks, how long they will persist after setbacks, and how effectively they will perform.
Bandura identified four sources of self-efficacy: mastery experiences (succeeding at difficult tasks builds efficacy; failure erodes it), vicarious modeling (seeing people similar to yourself succeed raises efficacy), social persuasion (being told by credible sources that you can do something), and physiological states (the interpretation of physical arousal as confidence rather than anxiety). Of these, mastery experience is by far the most powerful and most durable.
Napoleon Hill's principle of applied faith is, in psychological terms, an account of how to maintain self-efficacy in the face of setbacks: by focusing on past mastery experiences, by carefully choosing the people in one's mastermind alliance who model success, and by deliberately managing the interpretations placed on difficulty. The science and the philosophy are, in this case, describing the same phenomenon from different directions.