Without exception Matt Galligan’s internal clock nudges his body awake at 6:30 a.m., give or take 20 minutes. “If I go to a bachelor party in Vegas and I’m out until 6 in the morning, I still wake up at 6:30 a.m.,” the CEO of Circa , a popular news app, told Fast Company. “I can’t change.”

Set an alarm for the same time every morning for 30 days and resist the snooze button.

Galligan taught himself to wake up without an alarm clock about seven years ago, when he first learned about body clock training. The process is simple: Set an alarm for the same time every morning for 30 days and resist the snooze button. Beware: Waking up early for an entire month, including weekends, results in a lifelong dedication to being a morning person.

Our alarm clocks don’t care about circadian rhythms. Often, the marimba goes off in the middle of a REM cycle, which makes us feel groggy and grumpy about the day ahead. The snooze button feels like the best and only option–but it makes things worse by getting those sleep hormones going again.

Body training, however, teaches our bodies to work on our schedule. Here’s Mental Floss on the science behind the habit:

If you follow a diligent sleep routine–waking up the same time every day–your body learns to increase your PER levels in time for your alarm. About an hour before you’re supposed to wake up, PER levels rise (along with your body temperature and blood pressure). To prepare for the stress of waking, your body releases a cocktail of stress hormones, like cortisol. Gradually, your sleep becomes lighter and lighter.

If you do that enough, like 30 days in a row, then your body will wake up without any loud beeping noises to interrupt sweet dreams.

Galligan is either a cautionary tale of the practice or a miracle of science, depending on your view of ungodly hours. He’s a walking alarm clock. Even if he wants to sleep in, he can’t. “95 percent of the time it’s fantastic. I wake up very energized,” he said. The other 5 percent of the time there’s a lot of coffee involved.

For Galligan, those party-related inconveniences are worth it. He is a morning person, and gets his best work done between the hours of 6:30 and noon. Waking up refreshed each morning is the beginning of a very elaborate hours-long routine to get his brain ready for the day. He doesn’t look at his phone, which he doesn’t need to keep near his bed as an alarm clock, until after 9 a.m. The time before that, he spends making coffee, getting ready, and reading comics. Only after that, and a good night’s sleep, does he feel refreshed and ready to tackle the creative problems of the day.