Freud developed the idea of a series of developmental phases in which the libido fixates on different erogenous zones—first in the oral stage (exemplified by an infant's pleasure in nursing), then in the anal stage (exemplified by a toddler's pleasure in controlling his or her bowels), then in the phallic stage, through a latency stage in which the libido is dormant, to its reemergence at puberty in the genital stage.
Freud pointed out that these libidinal drives can conflict with the conventions of civilised behavior, represented in the psyche by the superego.
Sexual desires are often an important factor in the formation and maintenance of intimate relationships in humans.
It is the instinct energy or force, contained in what Freud called the id, the strictly unconscious structure of the psyche.
However, the levels of testosterone increase at menopause and this may be why some women may experience a contrary effect of an increased libido.
Certain psychological or social factors can reduce the desire for sex.
A person may have a desire for sex, but not have the opportunity to act on that desire, or may on personal, moral or religious reasons refrain from acting on the urge.
Psychologically, a person's urge can be repressed or sublimated.
Changes in the sexual desires of any partner in a sexual relationship, if sustained and unresolved, may cause problems in the relationship.