Hey, I do the same thing and I'm in my early 40's. I stuck a nice looking "chalkboard" sticker to my machine, and I use a chalk pen to write whatever notes I need to leave for myself on that. It's bold and hard to miss, and easily rubs off with my thumb.
I've always had a terrible memory though; it's not an age thing for me, it's just how I'm put together. I've ALWAYS been forgetful.