How does memory work? I really don't know. It seems logical that you remember the important events in your life: your child's first spoken word, scoring the winning goal, that time I left my car keys in a foreign country. You probably remember these events because you make an effort to do so. Memories will be reinforced by constant re-telling of the events by you or by friends & family. However, even for those important events it is possible for memories to be wrong. Two people can have a shared experience and yet their respective memories of the sequence of events can differ. That can be a heady mix at this time of year, just add the stress brought on by all the preparations and some Christmas spirits and voilà: a barney.
I don't require a long period of time to elapse for me to forget things. One of my least favourite memory failures is to completely forget someone's name, only ten minutes after being introduced. I tried a technique of repeating the name several times in my head, this succeeded in me remembering the name but completely missing what people were saying to me. Forgetting something is easy, being unable to banish a memory is much more frustrating.
The truly inexplicable situation is why I store detailed memories of completely random and unimportant events. A case in point was a Christmas shopping trip I undertook thirty years ago. Nothing important happened on this day out, yet I have a vivid memory of everything that happened, including details of what I was wearing (black brogues, black chinos, black turtle neck sweater, tan suede jacket) and even what I was listening to on my "walkman" (Wet Wet Wet - Popped in, Souled out). I just have no explanation why I have committed this trivial event to my memory, particularly in such detail.
There are even little mind's-eye videos, where I re-play the items I perused in an Edinburgh department store (John Lewis). It seems, I've been possessed by the Shopping Channel. At least with a TV you can choose not to switch on or to change the channel but I have no such control with memories. One minute I can be thinking about something unrelated, then I'll see a black turtle neck sweater and suddenly I'm transported back to 1987. It is my own wee Groundhog Day, which I am destined never to escape.