The psychologist Daniel Kahneman, who died last month aged 90, was perhaps most famous for his dictum that: ‘Nothing in life is as important as you think it is when you are thinking about it.’ This is often known as the focusing illusion.

The theory explains, say, why a recent Lottery winner with bad toothache may, in the moment, be little happier than a skint person with bad toothache, since in both cases their attention is focused on the pain, not their financial situation.