So I have this theory about how our brains hold everything. Since a picture says a thousand words, and I know you don't want to read a several-thousand-word post, I decided to illustrate my point. Literally.
As you are going throughout your day, everything you experience and learn goes right in here:
This is a much larger container. It can fit a LOT of days' worth of memories. So if you forget to put something into your brain storage system that you really wanted to keep, you can go dumpster-diving in here and get it back.
You need to be aware of two things, though. First, your memory of that-blog-post-that-filled-in-the-missing-piece-to-the-scene-you-were-working-on might have gotten the memory of the-one-piece-jumper-suit-you-saw-someone-wearing-and-made-you-fear-they-might-be-coming-back-in-style spilled all over it. Second, all those new memories that get poured into this bin every night fall on top of all the other memories there, pushing everything down a bit. The ones at the very bottom get pushed out that tube, and fall right out of your brain. So you don't want to wait too long to go dumpster diving, or it'll be lost forever.
Okay, so once you pull out a memory you want to keep, you need to store it. Different people have different ways of storing this information. There are shelves lining the entire perimeter of your brain that you can store stuff on. Some people put all their memories into nice, organized boxes, with labels on the front so that when they need to pull out a memory of, say, when is the correct time to use laid, lain, or lay, they can go right to the correct box and pull it out.
Sure, you can put lots of stuff in it, but when you're not looking, memories can slip out through those giant holes and fall right to the floor. Even the nice, neat, cardboard boxes can be an issue.
If you're not paying much attention to what's in that box, it can get water damaged. Or nibbled on by mice. Or torn. And memories can fall right out. (Yeah, I'm looking at you, rotted Trigonometry box.)
And if you don't notice that the memories have fallen out, the night crew sweeps them up and dumps them right back into here.
So make sure you label your boxes well, and keep checking on those ones that are really important! Otherwise you have to rely on being perceptive enough to know when to go dumpster diving, or those things you learned / experienced / loved might just be pushed out.