There are plenty of science-backed aways to improve your memory and recall. Using interleaving to learn several subjects or skills in succession. Taking simple steps to consolidate and reconsolidate memories. Exercising before you try to learn something new. Even sleeping–yes, sleeping–your way to better long-term memory and retention.

No matter how hard you try, that still doesn’t mean you’ll remember everything you want to remember.

And that’s a good thing, because a study recently published in Cell Reports shows forgetting things is actually an active part of learning and memory maintenance. As the researchers write:

While forgetting is commonly considered a deficit of memory function due to its association with pathological states, an alternative emerging perspective considers forgetting as an adaptive function of the brain that may contribute to learning and memory updating.

Recent findings suggest that forgetting is an active process that involves new plasticity that modulates the functionality of specific memory traces in order to promote adaptive behavior.

Or, in non researcher-speak: Updating your memory involves your brain doing a little strategic forgetting. 

Research indicates “forgotten” memories are still there. Instead of being erased, they just get “demoted” to a dormant state. In part, that’s why recognition is always easier than recall. Since I’m extremely forgettable, you may not be able to come up with my name when we meet for a second time (recall), but might immediately think, “Oh yeah, that’s right,” when I re-introduce myself (recognition.) 

How to Revive “Old” Memories

While the study involved a lot of fancy stuff–engrams and doxycycline and the dreaded hippocampus dentate gyrus–the key is brief re-exposure to whatever you previously learned.

Say you spent time yesterday learning the first section of a sales presentation. Today, before you move on to learning the next section, spend a few minutes reviewing what you learned yesterday.  A 2016 study published in Psychological Science found that people who studied before bed, slept, and then did a quick review the next morning not only spent less time studying, they also increased their long-term retention by 50 percent. (Sleeping on it not only helps your brain file away what you learned, but it makes that information easier to access.)

An earlier study published in Psychological Science shows that “distributed practice” is a much more effective way to learn. Each time you attempt to retrieve something from memory, the retrieval is more successful–what psychologists call study-phase retrieval theory–and that memory gets easier to retrieve. 

To keep learning and adapting, your brain needs, if not to forget, to shift some memories to a dormant state. That means learning can’t be one-and-done. You can’t learn something today and assume you’ll retain it forever. You’ll need to briefly review. You’ll need to re-activate older memories.