Self-belief does not necessarily ensure success, but self-disbelief assuredly spawns failure.

People who are insecure about themselves will avoid social comparisons that are potentially threatening to their self-esteem

Once established, reputations do not easily change.

Reasonably accurate appraisal of one's own capabilities is, therefore, of considerable value in successful functioning. Large misjudgments of personal efficacy in either direction have consequences. People who grossly overestimate their capabilities undertake activities that are clearly beyond their reach. As a result, they get themselves into considerable difficulties, undermine their credibility, and suffer needless failures. Some of the missteps, of course, can produce serious, irreparable harm

People who underestimate their capabilities also bear costs, although, as already noted, these are more likely to take self-limiting rather than aversive forms. By failing to cultivate personal potentialities and constricting their activities, such persons cut themselves off from many rewarding experiences. Should they attempt tasks having evaluative significance, they create internal obstacles to effective performance by approaching them with unnerving self-doubts

Judgments of adequacy involve social comparison processes

[Children] receive direct instruction from time to time about the appropriateness of various social comparisons