system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we lose some memories even if they are long-term memories?

If we can remember something like a name or number for months or even years, how can we eventually lose that memory after some period of time, however long it might be? What actually changes in the brain to make us forget?
gpt
Memories are "stored" as the connections between brain cells. These connections become stronger through use and weaker through disuse. 

If you don't think about something for long enough, the lack of activity causes the physical connection between cells that represent the memory, or a part of it, to weaken until it can no longer "store" that memory, or even will sever entirely.