One's self-perception is defined by one's self-concept, self-knowledge, self-esteem, and social self.
One's self-concept (also called self-construction, self-identity, self-perspective or self-structure) is a collection of beliefs about oneself. Generally, self-concept embodies the answer to "Who am I?".
One's self-concept is made up of self-schemas, and their past, present, and future selves.
Self-concept is distinguishable from self-awareness, which refers to the extent to which self-knowledge is defined, consistent, and currently applicable to one's attitudes and dispositions. Self-concept also differs from self-esteem: self-concept is a cognitive or descriptive component of one's self (e.g. "I am a fast runner"), while self-esteem is evaluative and opinionated (e.g. "I feel good about being a fast runner").
Self-concept is made up of one's self-schemas, and interacts with self-esteem, self-knowledge, and the social self to form the self as whole. It includes the past, present, and future selves, where future selves (or possible selves) represent individuals' ideas of what they might become, what they would like to become, or what they are afraid of becoming. Possible selves may function as incentives for certain behavior.
The perception people have about their past or future selves relates to their perception of their current selves. The temporal self-appraisal theory argues that people have a tendency to maintain a positive self-evaluation by distancing themselves from their negative self and paying more attention to their positive one. In addition, people have a tendency to perceive the past self less favorably (e.g. "I'm better than I used to be") and the future self more positively (e.g. "I will be better than I am now").
Psychologists Carl Rogers and Abraham Maslow had major influence in popularizing the idea of self-concept in the west. According to Rogers, everyone strives to reach an "ideal self". Rogers also hypothesized that psychologically healthy people actively move away from roles created by others' expectations, and instead look within themselves for validation. On the other hand, neurotic people have "self-concepts that do not match their experiences. They are afraid to accept their own experiences as valid, so they distort them, either to protect themselves or to win approval from others."
The self-categorization theory developed by John Turner states that the self-concept consists of at least two "levels": a personal identity and a social one. In other words, one's self-evaluation relies on self-perceptions and how others perceive them. Self-concept can alternate rapidly between the personal and social identity. Children and adolescents begin integrating social identity into their own self-concept in elementary school by assessing their position among peers. By age 5, acceptance from peers significantly affects children's self-concept, affecting their behavior and academic success.