Breathe through your nose

Watch a sleeping baby. Its mouth is shut and its belly rises and falls. That is how we all breathed before something went wrong, and for most of us something did, somewhere around the age of a blocked nose, a dummy and a soft diet.

Bear has a line about this that is hard to forget. Mouth breathing is an emergency airway promoted to full-time employment. The mouth is for when you are sprinting or drowning. The nose is for everything else, and it is built for the job in ways the mouth is not. It filters the air, warms it, adds moisture and slows it down, so that by the time it reaches the lungs it is the right temperature and the right speed and most of the rubbish has been caught on the way in.

Breathe through your mouth all day and none of that happens. You also tend to breathe faster and shallower, which the body reads as mild alarm, and so you feel slightly on edge for no reason you can name.

The fix is unglamorous. Shut your mouth. Notice when it is open, on the school run, at the desk, on the sofa, and close it. Nose in, nose out, for as much of the day as you can manage.