Some people wonder where depression originates from. There is no answer to that question because depression is the natural state. The reason is in our consciousness. If conscious enough to understand how pointless life is, you cannot but be depressed.
Therefore evolution provided us with an intricate rewarding system that allows to enjoy life. For instance, like other animals, we enjoy the pleasure to eat, to have sex, and to interact socially (social grooming). Also as humans, our societies evolved a rewarding system. For instance, institutions exist that reward with pleasure or limit consciousness.