Mark Divine was at his breaking point.

After five and a half days of sleep-deprived torture by the surf, Divine was singled out by a Navy SEAL instructor overseeing his BUD/S training. The instructor ordered him to perform 1,000 “body builders,” an 8-count burpee-like movement. Somewhere around his 700th rep, Divine realized he was about to fall apart. But he instead forced himself to start smiling and laughing—a technique to draw out positive energy in a desperate moment.

It worked. “Soon I was feeling 100 percent better, as if bolts of lighting were flowing through me,” Divine later wrote. He passed the test, having dug deep into a reservoir of mental toughness when things were hellaciously bleak.

Divine went on to serve as a SEAL for 20 years and later launched SEALFIT, a training center in Encinitas, Calif. He recounts this experience in a new book The Way of the SEAL ($15.04, Reader’s Digest Books). Focusing on developing mental toughness, Divine offers up stories and methods he personally used in some of the more trying circumstances he faced as a SEAL and in his martial arts training (he holds black belts in Seido and Goju Ryu Karate, as well as teaching expertise in Ashtanga Yoga).

Drawn from his SEAL, yoga and martial arts backgrounds, the book offers a set of tools to help readers establish and clarify their purpose and values, goal-setting techniques and methods to build their powers of intuition. He also discusses how to achieve goals and objectives in a very high-speed, Navy SEAL sort of way.

In the book, Divine says readers can use periodic challenges to break out of ruts, rid themselves of lazy, complacent training habits and build vast amounts of mental toughness. He recalls how Navy SEAL instructors beat into the minds of trainees that they are capable of “at least 20 times what you think you are!”

“A unique, if unfair, aspect of our beautiful human condition is that if you avoid challenge, it will come anyhow, bringing with it severe and painful lessons,” Divine writes. That’s why he suggests going on offense.

“Take yourself to the challenge rather than waiting for it to come to you,” Divine writes.

10 SEALFIT Challenges that Test and Build Your Mental Toughness

While minor challenges can be planned throughout your week to replace bad habits with good ones or improve the quality of your training effort, major challenges can be planned for either monthly or quarterly. They should be within reach of your current level of fitness, Divine says. “Don’t do anything dumb,” he writes, adding that anyone starting a new fitness program should first get the OK from a medical doctor.

Use these challenges as opportunities to practice your mental skills, like staying positive when things get hard and focusing on the moment. Likewise, choose a goal that is a true challenge—something that will push you outside your comfort zone.

Training Challenges

Record your effort so  you can check your progress.

1. Run-Burpees-Run. Perform 10 rounds of the following sequence: 100 burpees, run 800 meters.
2. Perma-Plank: Hold a plank for 10 minutes without failing or sagging.
3. 1,000 Pull-Ups for time: Have a nice day!
4. The Longest Mile: Carrying dumbbells at your side or wearing a weighted vest, perform Walking Lunges until you’ve covered a mile.
5.  2,500 squats for time: Bodyweight Squats will be fine. You’ll feel it, trust us.

Event Challenges

Sign up and train for one of the following events.

1. Run a marathon.
2. Enter and complete a Spartan race.
3. Finish a half-Ironman triathlon.
4. Climb a mountain.
5. Enter a 200-mile bike ride.