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
Albert BanduraA theory that denies that thoughts can regulate actions does not lend itself readily to the explanation of complex human behavior.
Albert Bandura