Waking up at 7:00 AM might feel great one day and terrible the next. The difference isn't how much you slept, but *when* you woke up.
Human sleep occurs in cycles of roughly 90 minutes. If you wake up in the middle of a cycle (Deep Sleep), you'll feel groggy and "sleep drunk." If you wake up at the end of a cycle (Light Sleep), you'll feel alert immediately.
To feel your best, you should aim for 5 or 6 full cycles (7.5 or 9 hours). Use our Sleep Calculator to find your optimal bedtime based on when you need to wake up!