system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 how we are able to remember that we've forgot something, but not remember what we've actually forgot?
gpt
You may give yourself a cue to remember something.  The cue itself is a separate memory.  You may have mentally concentrated more on the cue so you wouldn't forget, than you did on the thing you were trying to remember.  

Example: you have laundry in the washer, and you decide to get started on mowing the yard, but tell yourself to remember to go back in the house and move the laundry into the dryer after you run the lawnmower through one tank of gas.  

Several times as you mow, you think ahead to how much mowing you have left to do, and each time you do, the thought goes through your head that the first time you run out of gas, you must attend another task, and the first step of that task being to go back into the house, that's the part that crosses your mind, and it gets more fixed in your memory.  

Finally, you do run out of gas, you go back into the house, and... you can't recall what it was you were going to do when you got there.