Myth 1: 'I must get 8 hours or the day is ruined.' Pressure about sleep is itself a stimulant. Ranges vary; bad nights happen and bodies compensate.
Myth 2: 'Lying in bed awake is still rest.' After ~20 wakeful minutes, get up and do something calm in dim light — beds should mean sleep.
Myth 3: 'Alcohol helps me sleep.' It helps you fall asleep, then fragments the second half of the night.
Myth 4: 'Naps are bad.' Short early naps are fine for most people; long late naps borrow from the night.
Myth 5: 'I should catch up massively on weekends.' Large swings jet-lag your body clock. Keep wake times within about an hour.