What a nightmare!

After trying a warm glass of milk, reading a book, and counting sheep, if the Sandman still hasn’t arrived, you’re not alone. For many Americans, it takes about half an hour to fall asleep, which is longer than ideal.

A five-minute trick may save you precious time — and sheep. Before hitting the hay, try writing a list of tasks to tackle the following day.

“When I started making nightly to-do lists, I didn’t have any idea it was going to help me sleep — I just wanted a way to better track my priorities and productivity from day to day,” CNET managing editor Adam Benjamin penned last week.

“So every night before bed, I would write down three things I wanted to do the next day,” Benjamin continued. “I would also note one good thing that happened during the day, no matter how small.”

There’s science to support the slumber suggestion. A 2017 study found that participants who wrote a to-do list before bed instead of journaling about their accomplishments fell asleep “significantly faster.”

Nine minutes, to be exact, which the Baylor University researchers confirmed with a diagnostic test.

“The more specifically participants wrote their to-do list, the faster they subsequently fell asleep, whereas the opposite trend was observed when participants wrote about completed activities,” the study authors wrote in the Journal of Experimental Psychology.

They speculated that writing down tasks lets you jettison your worries, so you don’t need to think about them while trying to sleep.

The concept is called “cognitive offloading.” It reduces the mental effort required to complete an assignment, which can ultimately lead to better performance.

Examples include writing down a grocery list, setting a reminder on your phone about an upcoming appointment and leaving an item in a specific place to remember it later.

The importance of “cognitive offloading” was shown in a 2014 study of German IT workers. Employees who didn’t complete tasks by the end of the week had worse sleep over the weekend because they spent so much time fretting about the unfinished business.

Sleep experts who spoke to CNN recommended scheduling a “worrying time” outside the bedroom to explore concerns that may keep you up at night and emailing yourself your to-do list.

“It gives you satisfaction and the realization that it is night and there’s nothing you can do with your list, but you can attend to it tomorrow,” Dr. Vsevolod Polotsky, a sleep medicine physician, told the outlet.