Forgetting is no mere vis inertiae as the superficial imagine; it is rather an active and in the strictest sense positive faculty of repression, that is responsible for the fact that what we experience and absorb enters our consciousness as little while we are digesting it
Nietzsche redefines forgetting as an active, positive psychic capacity—a form of healthy repression that protects consciousness from being overwhelmed by undigested experience.
, On the Genealogy of Morals, 1887thesis