Four. The three compensations

These came up in lesson two and they are worth the second pass, because they are the hardest to give up.

Going to bed earlier. Lying in. Napping late in the day. Each is the obvious response to being tired, and each one takes sleep pressure out of the evening and puts more awake time into the bed.

A short early afternoon nap, twenty minutes or so, is usually fine and can be genuinely useful. An hour on the sofa at six is not, because it spends the pressure you needed at eleven.

And one thing to know before you start blaming yourself for the two o'clock waking: everybody surfaces several times a night. Most people simply do not remember it. What turns a normal waking into an hour of being awake is what happens next, which is the arithmetic.