Sleeping well for an entire night, without waking up once, seems to be a surprisingly rare thing, but it’s actually what’s required if you’re to be entirely productive – without feeling tired – the next day.

Many people think that simply going to bed at the right time guarantees them a good night’s sleep, only to then wake up – more often than not – between 3:00am and 5:00am. Sometimes this can cause problems, particularly when someone finds it difficult to return to sleep.

The fact that most people wake up during this window isn’t coincidence, however, nor is down to bad luck. It turns out, there’s a significance to the trend …

The hours between 3:00am and 5:00am are sometimes referred to as the hour of the wolf, after Swedish director Ingmar Bergman’s psychological horror[film of the same name.

”The hour between night and dawn … when most people die, sleep is deepest, nightmares are most real. It is the hour when the sleepless are haunted by their worst anguish, when ghosts and demons are most powerful. The hour of the wolf is also the hour when most babies are born,” Bergman explained.