Since sleep cycles last about 90 minutes, I felt better waking up between cycles (4.5 hours is about 3 complete cycles) than waking up in the middle of a sleep cycle (8 hours is 5.3 cycles). It turned out that this phenomenon was called "sleep inertia."
I read this too and while I've not been so good these past three weeks, prior to that I've been sleeping as close to exactly 7.5 hours as possible and for the first time ever, I was able to consistently get up at 6:30 each morning without tiredness or finding it hard to get up. I picked 7.5 hours so that I'd have a good long sleep to take me through busy & stressful days, but on nights when I wasn't able to get to bed by 11pm, I picked a shorter multiple of 90 minutes and it works just as well except that if its too short over all, I start feeling drowsly earlier in the day.
I read this too and while I've not been so good these past three weeks, prior to that I've been sleeping as close to exactly 7.5 hours as possible and for the first time ever, I was able to consistently get up at 6:30 each morning without tiredness or finding it hard to get up. I picked 7.5 hours so that I'd have a good long sleep to take me through busy & stressful days, but on nights when I wasn't able to get to bed by 11pm, I picked a shorter multiple of 90 minutes and it works just as well except that if its too short over all, I start feeling drowsly earlier in the day.
I really need to do this again.