Three old ladies are sitting in a diner, chatting about various things.
One lady says, "You know, I'm getting really forgetful. This morning, I was standing at the top of the stairs and I couldn't remember whether I had just come up or was about to go down."
The second lady says, "You think that's bad? The other day, I was sitting on the edge of my bed and I couldn't remember whether I was going to bed or had just woken up!"
The third lady smiles smugly. "Well, my memory's just as good as it's always been, knock on wood."