"Moreover, if the 'regression-compulsion' in all organic life is striving for integral quiescence, if the Nirvana principle is the ground of the pleasure-principle, then the necessity of death appears in an entirely new light. The death instinct is destructiveness not for its own sake, but for the relief of tension. The descent toward death is an unconscious flight from pain and want. It is an expression of the eternal struggle against suffering and repression."
Herbert Marcuse Eros and Civilization (1956 [1998]) p.29