Why does the habit of poor sleep continue even after the initial cause is long gone?
Once you begin to sleep poorly, you lose confidence in your ability to sleep well. You
may begin to fear going to bed. You may become tense, and you may begin to worry
about "not sleeping". In addition, your body clock may have become wrongly adjusted.
That is, your body may now be in the habit of not falling asleep until the early hours of
the morning, or it may be in the habit of waking at 1am or 3am, or it may be in the habit
of waking frequently each night.