Memory is one of the weirdest things about the human experience, it's still relatively unknown how we store and "revisit" memories on some levels, and our memories are not records like photographs or data on a hard-drive, they're really more like saved simulations that you rerun every time you bring them up, this is why they can be so radically wrong or distorted from actual events. Every time you run that simulation your brain will "smooth out the edges" and fill in gaps with whatever it predicts should be there.

Your brain is so good at doing this, that you can easily wire yourself to have false memories. Most people are unsettled by this prospect but you can use it for fun! Example: I have altered my own memory of the 2004 disaster film "The Day After Tomorrow" to also include Frankenstein's Monster as one of the dangers of the frozen world, and have clear memories of Frankenstein's Monster clomping around with his pack of wolves looking for the protagonist. Great movie, highly recommend you watch and re-write in your mind.