"For the first time, Stanford researchers using functional magnetic resonance imaging (fMRI) have discovered that the brain's ability to suppress irrelevant memories makes it easier for humans to remember what's really important. "
It seems our memories are finite after all. This research essentially shows that our prefontal cortex actually aids new memory formation and recall by "deleting" or forgetting less important details. It's kind of like the saying, "When something goes in, something else has gotta come out". I must be an exception to the rule, because it's not usually not the usual meaningless things that go with me, it's usually the really important things that I forget.
"According to Wagner, the findings demonstrate the brain's ability to discard irrelevant memories. "Any act of remembering re-weights memories, tweaking them to try to be more adaptive for the next time you try to remember something," he said. "The brain is plastic—adaptive—and one feature of that is not just strengthening some memories but also suppressing or weakening others." "