Personal development comprises activities that improve self-knowledge and identity, develop talents and potential, enhance quality of life and realise dreams and aspirations. The concept of personal development covers a wider field than self-development or self-help; it also includes developing other people, and by extension refers to the methods, programs, tools, techniques, and assessment systems used in personal development. From early advocates in self-driven advice, the connotations of the phrase have spread and often apply particularly to education, business, or psychological areas, purveyed through the popular genre of self-help books. Dale Carnegie (1888-1955) is sometimes credited with beginning the self-help movement in the twentieth century when he published How to Win Friends and Influence People in 1936. Having failed in several careers, Carnegie became fascinated with success and its link to self-confidence, and studied the subject for years. Carnegie's books have since sold over 50 million copies, alongside modern bestsellers in the field such as Wayne Dyer, Louise Hay and Anthony Robbins.