Jung believed that the psyche is a self-regulating system, rather like the body, one that seeks to maintain a balance between opposing qualities while constantly striving for growth --journalpsyche.org
Freud theorized "young girls experience anxiety upon realization that they do not have a penis. Freud considered this realization a defining moment in a series of transitions toward a mature female sexuality". --Wikipedia. Freud's work is at 499 in TvF.