All bow to the wisdom of Wife
For years I have had issues with sleep. I don't sleep much at one time. Maybe 5 hours. I compensate by take a couple of naps a day when I can get them. Particularly infuriating has been a pattern.
On days when I have to get up early (for me around 4 AM), I will set my alarm. On those days, I seem to sleep particularly deeply. I will be in the deepest sleep when the alarm goes off. Then on the days when I can sleep late, I don't set the alarm. But instead of sleeping deeper or later, I tend to not sleep as well and am always up early anyway.
Wife suggested that maybe there was something psychological going on. Her thought was when I set the alarm I can relax knowing I will be woken up and can therefore go into a deeper sleep. But when I don't set the alarm, I somehow am less relaxed and therefore don't get into such a deep sleep.
This weekend I had three days in a row where I didn't have to get up a a particular time. On Friday I set the alarm for a time much later than I would normally get up. Indeed I slept straight through until the time the alarm went off. On Saturday, I did not set the alarm and I had a very disrupted, not restful sleep. On Sunday, I again used the alarm set to a later time and had the same deep, later awakening sleep as on Friday.
Could this be a breakthrough in sleep? I hope so.