I am healthy and full of energy.

A surprising amount of tiredness is not physical. It is the cost of carrying something undone — the call you have been avoiding since Monday, which will take four minutes and has been quietly billing you for six days.

People notice this in reverse. They make the call, the rest of the afternoon is inexplicably lighter, and they credit the coffee.

Not everything works that way, and some tiredness has causes no list will fix. But it is worth checking whether one item on yours is drawing more than it costs.