The friend who shows up with jumper cables at midnight is richer than anyone with a bigger car.

Wealth is being measured here in something other than money: who actually turns up when it is inconvenient. A person with nothing to gain, driving across town at midnight, is spending the one currency that cannot be faked. Plenty of people can afford a nice car. Far fewer will lose a night of sleep for you.

Make a short mental list of who your midnight people are. Then ask whether you are on anyone else’s list. If you are not sure, the way in is simple: be the one who answers the inconvenient call this month.