This was my grandfather's favourite tale on old people with set habits:

Two old men were sitting on a park bench (a la Aqualung?) one morning. One said to the other, "You know, habits are so difficult to break at our age. For instance, it's become my habit to go home after the morning walk and have a cold beer, whether there's some at home or not."

The second man was most intrigued; "How can you have a beer if there's none at home?"

Said the first old man forlornly, "That's what I was talking about - (sigh) habit!'