Here's the habit I just can't break - even though it could be sabotaging my sleep

For the past two months, I've been experimenting with a new daily routine suited to my unique biological makeup.

That unique biological makeup is also known as a "chronotype," or a predisposition to be a morning person, an evening person, or somewhere in between. Scientists say your perfect schedule depends heavily on your specific chronotype.

According to Dr. Michael Breus, a psychologist and sleep specialist and the author of "The Power of When," there are four different chronotypes: bear, wolf, lion, and dolphin. (You can take a quiz to find out which animal best describes you here.)

As it turns out, I'm a "bear," meaning my internal clock tracks the rise and fall of the sun.

By and large, the daily routine experiment was a success: Once I started waking up later and delaying my cup of caffeinated tea until after 9:30 a.m., I felt more energized and productive.

At the same time, I completely failed to make one of the most important changes Breus recommended when we spoke by phone in July: instituting what he calls the "power-down" hour. About 60 minutes before you go to bed, Breus advises staying off social media and putting away most digital devices. Instead, you can read a book or meditate.

It sounded sensible, and pretty easy. But alas, I couldn't stay off Facebook and Instagram at night. #chronotypefail.

Recent research on college students suggests that using digital technology in the hour before bed contributes to poorer-quality or disrupted sleep. (Interestingly, other research has found that using social media in general - not just at night - is linked to sleep disturbance among young adults.)

When we spoke in July, Breus told me that using social media before bed can be problematic for two reasons. First, the blue light emitted from digital devices can interfere with the production of the sleep hormone melatonin, which makes it harder to fall and stay asleep.

Second, the content on social media - all those vacation selfies and self-promotional status updates - can be emotionally stimulating, which can also disrupt sleep.

I knew what he meant - I spent an hour the other night scrolling through my friend's Instagram photos of African animals and subsequently had a nightmare about being chased by a cheetah.

Still, breaking the habit of grabbing my iPhone and scrolling through my newsfeed was harder than it seemed at first.

Maybe it's because the post-dinner period is generally the first time all day when I don't have an activity planned - meaning it's the first opportunity I have to be bored. And boredom may be a key trigger for the Facebook habit.

When we spoke again in August, Breus told me he thinks browsing photos and updates on Facebook and Instagram stimulates the release of dopamine, a neurotransmitter related to feelings of reward and pleasure. So in a way we become "addicted" to that release, and to social media.

That's why Breus said I'm hardly alone; sticking to the power-down hour is one of the hardest changes for his bear patients to make.

At the same time, his experience with patients - especially bears - has taught him that people really "turn the corner" when they stop using their digital devices late at night.

One way to make that change easier, Breus said, is simply to set an alarm for an hour before bed and then move your phone (and other gadgets) to another room. It might take a few days, if not a few weeks, to get used to.

"Of the patients that are able to succeed in doing it," Breus said, "they say it is one of the most freeing experiences because they're like, 'Oh my gosh. I'm not tied to my phone.'"