The Pygmalion Effect explains that people tend to perform up to the level that others expect of them. This effect explains why our
relationships are usually self-fulfilling prophecies. Once you set
expectations for somebody, that person will tend to live up to that
expectation, whether it's good or bad.
But the Pygmalion Effect also applies to your personal growth. Your beliefs about yourself impact your actions towards others, which influence their beliefs about you and their actions towards you.