The number one archenemy of the memories you’ve created and stored is time. It’s not enough to pay attention to an experience, pluck some pieces of sensory information and emotion from it, bind them together into a singular memory, and then store that memory through alterations in synaptic connections between the neurons that were originally activated by that experience. If you don’t revisit the memory, if it just sits on your brain’s cortical shelf like an old trophy collecting dust, that memory will erode with the passage of time.