Of course, there are unhealthy kinds of forgetting. Alzheimer’s disease, for one, targets memory mechanisms and causes them to fail. But in other disorders, it appears that the brain’s forgetting mechanisms break down. The psychological condition that perhaps best exemplifies what can happen when people don’t forget properly is PTSD. While it is often beneficial to remember the facts of a traumatic experience, sometimes even in pointillist detail, it is equally — if not more — important to the healing process to let the emotional valence of it fade. If we don’t, we can get stuck in total emotional recall, reviving our distress in perpetuity.

Forgetting protects us from this debilitating anxiety not by deleting memories but by quieting their emotional scream. The same is true for more run-of-the-mill emotions. Intuitively, it makes sense that we sometimes need to “let go” of hurt and resentment to preserve close friendships and that we need to forget in order to forgive. “Letting go” is just one of the many colloquialisms that implicitly nod in recognition and gratitude toward our brain’s forgetting mechanisms.