According to Swiss psychiatrist Carl Gustav Jung, the libido is identified as psychic energy.
Duality (opposition) creates the energy (or libido) of the psyche, which Jung asserts expresses itself only through symbols: "It is the energy that manifests itself in the life process and is perceived subjectively as striving and desire." (Ellenberger, 697) Defined more narrowly, libido also refers to an individual's urge to engage in sexual activity, and its antonym is the force of destruction termed mortido or destrudo.
On the other hand, a person can engage in sexual activity without an actual desire for it.
Multiple factors affect human sex drive, including stress, illness, pregnancy, and others.
Problems can arise from disparity of sexual desires between partners, or poor communication between partners of sexual needs and preferences.