A day in the life of a retired Navy SEAL commander, who wakes up at 4:30 a.m., trains in Brazilian jiu-jitsu, and doesn't eat for 72 hours at a time

As the night winds on, Willink likes to spend some time with his family — he's a married father of four — and will often get some guitar playing in.

Willink has been a passionate fan of hardcore music since he was a young teenager, and has played the guitar since then, as well. "But I'm not good," he told us. "At all."

He'll sometimes get together with friends to jam.

When he gets home, it's time for dinner. Willink typically goes for steak and vegetables, and eats at 8:00 p.m.

In addition to his meals, Willink got his branding on a krill oil and joint health supplement because those are the supplements he's taken for some time. He's found that they are useful for recovery from jiu-jitsu training.

When the work day ends, it's time for Brazilian jiu-jitsu training. Willink is a black belt and is a BJJ trainer at a San Diego gym he co-owns.

A Navy SEAL master chief introduced Willink to Brazilian jiu-jitsu, and he fell in love with the sport.

He even goes so far as to say that it's the best martial art anyone can learn.

He told us: "Not only does it get you in good physical condition. Not only does it teach you how to defend yourself. ... It also is intellectually challenging and you constantly have to learn to adapt to new moves."

After his podcast became a hit last year, Willink began building a personal brand. His afternoons will often include managing his product partnerships and working on a book.

Willink, who goes for tea instead of coffee, decided to try his hand at his own line of his favorite drink — and it became a huge hit with his podcast fans, regularly selling out.

He also recently expanded a partnership with Origin USA, getting co-branding onto athletic gear, martial arts uniforms, and krill oil and joint health supplements.

And on top of that, he's been working on a constant stream of books since 2015's "Extreme Ownership" became a New York Times bestseller. He's currently working on both a new one with Babin and a sequel to his children's book "Way of the Warrior Kid."

Willink will meet up with his podcast producer Echo Charles at least once a week to hash out a podcast episode. Recording sessions run an average of three hours.

"We record when I have a hole in the schedule," Willink told us. "Sometimes night, sometimes afternoon, sometimes morning — we fit it in when we can. I prep for episodes all the time. Planes. Airports. Before I go to sleep. While eating lunch or dinner. I'm always reading the next book. Taking notes. Highlighting, researching, studying. It doesn't stop."

Willink skips breakfast but will have lunch between 11 and noon. He keeps it simple, typically eating grilled chicken and some vegetables.

Willink roughly follows the Paleo diet, which is essentially unprocessed, hormone-free meat, fish, vegetables, fruit, and nuts. It's a low carbohydrate diet.

He also has a fasting regimen, in which he'll do a 24-hour fast about once every two weeks and a 72-hour fast once per quarter.

Willink is always working with Echelon Front clients remotely or in-person, and the team periodically assembles for conferences.

Echelon Front has worked with clients like Shell Oil, Citi Bank, and the San Diego Padres Major League Baseball organization.

Willink and his colleagues will do group leadership training sessions or divide up individual clients.

On a typical day, Willink spends a chunk of the morning corresponding with his clients over email or the phone, or in person — he travels weekly for consultations.

After a shower, it's time to tackle his to-do list, which he prepared the night before. This often includes hours of research for his podcast.

"Every day is a major balancing act that I have to figure out and coordinate," Willink said, since he's always working on multiple projects simultaneously.

One of those projects is his weekly podcast, which is a wide-ranging exploration of military history, business leadership, and the lives of people Willink finds inspirational. The episodes are typically three hours long, and each requires 15-20 hours of research and preparation, since they are dense with historical and biographical information.

Willink takes advantage of living in San Diego, and regularly hits the beach after his workout for a quick surf session.

Willink grew up in Connecticut but moved to San Diego for the SEAL base there, and decided to stay. He likes to take advantage of living near the beach, and if it's not surfing weather, he might go for a run on the sand.

Then it's time to head to his garage, which he's converted to a full-blown gym. He'll work out for about an hour, not counting cardio.

Willink lays out his workout clothes before going to sleep each night so that he can get active as quickly as possible, regardless of whether he's feeling groggy or energetic.

He's got a four day workout rotation (pull, push, lift, squat), and each day's routine is preceded by a warm-up and followed with core exercises and cardio work. You can find a more complete breakdown of the routine on Business Insider, and an even more in-depth guide is in "Discipline Equals Freedom."

Willink wakes up every morning, even on the weekend, at 4:30 a.m.

It's a habit he picked up in the SEALs.

He wrote in his book "Extreme Ownership," cowritten with Babin, that he noticed as a young SEAL that the highest performers he served with were those who woke up earliest, beginning their days while everyone else slept.

To both hold himself accountable and inspire others, Willink posts a photo of his watch each morning to his Twitter page.