I think everyone has moments of forgetfulness. I once went shopping and walked home carrying the shopping only to realise that I had left the car in the supermarket car park.
Its just that as we get older they may happen a little more.

The Doorway Effect occurs because we change both the physical and mental environments, moving to a different room and thinking about different things. That hastily thought up goal, which was probably only one plate among the many we’re trying to spin, gets forgotten when the context changes.

Our brain organises our goals into a hierarchy of actions - but even the simple act of walking through a door may cause us to lose track of our plans

Imagine that we’re going upstairs to get our keys and forget that it is the keys we came for as soon as we enter the bedroom. Psychologically, what has happened is that the plan (“Keys!”) has been forgotten even in the middle of implementing a necessary part of the strategy (“Go to bedroom!”). Probably the plan itself is part of a larger plan (“Get ready to leave the house!”), which is part of plans on a wider and wider scale (“Go to work!”, “Keep my job!”, “Be a productive and responsible citizen”, or whatever). Each scale requires attention at some point. Somewhere in navigating this complex hierarchy the need for keys popped into mind, and like a circus performer setting plates spinning on poles, your attention focussed on it long enough to construct a plan, but then moved on to the next plate (this time, either walking to the bedroom, or wondering who left their clothes on the stairs again, or what you’re going to do when you get to work or one of a million other things that it takes to build a life).

And sometimes spinning plates fall.