I have a friend whose grandfather's mental state had slipped a gear. He was sharp, but his concept of time and place was shot. Even if he had not left the house for a week, when you asked him how he was doing, he would say with a smile, "Great! I just got back from playing cards at Caesars Palace with the boys." In his mind, he was always coming home from a good time. I think that must be a great mental space to be in.
Crazy Philadelphia Eddie was mentally sharp until the day he died, and he often talked about his trip to Copenhagen as a young man. It had everything a young man could want. Eddie found a country with cheap beer, bars that only closed for an hour a day, and plenty of women. Reflecting on this trip, Eddie told me, "Copenhagen, that was my city of love."