I think the first response is correct, and as aged people we've learned to do a couple of things at once, such as walking and thinking at the same time, often planning or anticipating what's likely to come next. It's a way to be more efficient. Unfortunately, in times of higher demand or stress, which is where you find yourself, we do a lot more of the latter and less of the former. We might place our keys in a place of no immediate concern, but of later consequence. What people 'should' do is to routinize much of what they do often so that it becomes more automatic. I always place my glasses, my keys, my wallet, and other things I use at least once a day in the same spot so that I can literally find them in the dark. This requires determination, motivation, and repeated practice so that it becomes second nature. This is hard to do when the demands on you are inordinate and many.