The other day I started a round of antibiotics and I keep not being able to remember if I took my last dose. I'm worried about forgetting to take one so it comes to mind often, and I go so far as imagining taking one before I actually do. Then the act of taking one is so quick that somehow the memory of taking a pill gets collapsed into the memory of anticipating taking it, such that I can't remember, five minutes later, whether I took a pill or whether I just imagined I did; I keep having to count how many are left.
That phenomenon, so concrete in the pill example, because the anticipated action is so brief and thus easy to forget, is a fascinating one and makes me wonder how much of our memories of actual events in our history are at least partially conflated with our memory of our anticipation leading up to the event, in which we imagined, perhaps many times, if we were excited or nervous, what the event would be like. It seems like an easy way for details to become shuffled, in retrospect.
I think particularly of the potent memories of childhood Christmases and wonder how much I am remembering those magical mornings themselves, versus the days and weeks leading up to Christmas, which were filled with anticipation and wonder.
When we greatly anticipate a thing, the thing itself becomes the culmination of all our imaginings, is but the top layer adorning a stack of imagined versions of the event itself. But we forget this when we recall it; we remember it as a single thing rather than the many that it is.