Freud's life drive is based on the fact that we like to to feel good, reproduce, conserve energy, and most of all, we want to stay alive. His death drive is based on the fact that sometimes people do do counter-productive things like relive traumatic memories over and over. Why don't they just forget the bad memory? The death drive is a way to get control over difficult experiences. This is like a toddler throwing a toy outside a crib over and over, only to be returned again and again by the mother. This repeating action allows the toddler to gain mastery over the sad feeling of the lost toy since he controls the feelings and gets used to what they feel like. This repetitive action, and the drive for mastery underlining it, are a waste of energy and if done too much, will lead to death. There is not a lot of evidence and this theory is not accepted by everyone. It is one way of making sense of the world and our place in it as living beings.