Cathexis is the libido's charge of energy. Freud often described the functioning of psychosexual energies in mechanical terms, influenced perhaps by the dominance of the steam engine at the end of the nineteenth century. He often described the libido as the producer of energies that, if blocked, required release in other ways. If an individual is frustrated in his or her desires, Freud often represented that frustration as a blockage of energies that would then build up and require release in other ways: for example, by way of regression and the "re-cathecting" of former positions (ie. fixation at the oral phase or anal phase and the enjoyment of former sexual objects ["object-cathexes"], including auto-eroticism). When the ego blocks such efforts to discharge one's cathexis by way of regression, i.e. when the ego wishes to repress such desires, Freud uses the term "anti-cathexis" or counter-charge. Like a steam engine, the libido's cathexis then builds up until it finds alternative outlets, which can lead to sublimation or to the formation of sometimes disabling symptoms.

See also, Psychoanalysis