doesn´t work for me - i have no clock in visible range of my bed. Instead most of the time i need to get up 5-20 times per morning, pushing the snooze button ( sometimes i think i´m some kind of lost-participant PUSH THE BUTTON EVERY 8 MINUTES.... ).
Why is that? My bedroomcurtains are not able to fully vanish the sunlight from the outside - so i know even when asleep how late it is.
But i also had this experience: wake up after 7.5 hours with alarm-clock: most of the day nearly falling asleep - often needing a nap. Waking up after a few hours on my own ( or my girlfriend waking me up ): totally refreshed and not any tired. How come?