But forgetting can also be caused by “retroactive interference,” which is when you experience two events that are quite similar close in time. The memory of one interferes with the other.

And certain kinds of forgetting is actually really good for us. Most of us have utter confidence in the veracity of our memories. "I remember like it was yesterday!" we say.

Forgetting allows us to adapt and improvise, and sleep is key to deleting extraneous cortical information. We dream in order to forget.