History Freud invites us to consider the history of humankind. He mentions various wars, persecutions, the Crusades, and other evidence that confirm the prevalence of aggression. This is the force that builds up. It combines units into larger wholes. Eros is constructive.
Sex is just one manifestation of the erotic instinct.
Death This is the force that tears down. It seeks release from tension and a return to earlier states. Death is destructive. Aggression is just one manifestation of the death instinct. For example, I want to be the same as my father or mother, or a political leader, or a hero, or a fictional character.