This video is part of Health's My Mantra series. Follow along with new videos on our Instagram page and share your own words of wisdom using #MantraMonday.

Sarah Michelle Gellar knows what it means to be motivated. The actress become a household name in the 1990s when she landed a starring role in Buffy the Vampire Slayer, and she's continued to steadily work in TV and film since.

With a busy career and parenting duties to handle, it's no surprise that she relies on a killer mantra to keep her going. Gellar tells Health why her mantra works for her (check out the video above!), and why she continues to harness its power.

RELATED: Sarah Michelle Gellar Reveals Postpartum Depression Struggle in Health Care Plea

"There was a quote from the musical Chess, the original production, that always stuck with me: ‘You taught me baby, how the few who win acquire, it ain’t practice, it ain’t skill, they’ll help, but not as much as wanting will.’ And I think for me, it encompasses everything, which is that you have to really want something in life to make it happen," explains Gellar.

"It’s not about waiting for something to come to you," she continues. "That if there is something you’re looking to do, something you’re looking to experience, those are moments you need to make happen for yourself."

Honestly, I think I probably use it every day, I remind myself I want to be better. To accomplish different things. To want to be more patient. Whatever those moments are, for me it’s about just keep it at the back of my head," she adds.

RELATED: Sarah Michelle Gellar on Shannen Doherty's Inspiring Breast Cancer Battle: 'That's What Real Bravery Is'

This is the first time Gellar has touched on her personal life. In 2017, the actress opened up about her battle with postpartum depression in an emotional Instagram post, explaining how the disease impacted her daily life. 

“Having kids is wonderful, and life changing, and rarely what you’re prepared for,” Gellar wrote at the time. “I love my children more than anything in the world. But like a lot of women, I too struggled with postpartum depression after my first baby was born.”

“I got help, and made it through, and every day since has been the best gift I could ever have asked for," she wrote. "To those of you going through this, know that you’re not alone and that it really does get better."

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Bad guys, take note: Here’s even more proof you need to be careful who you mess with—and it comes in the form of an 82-year-old bodybuilder.

Willie Murphy, a grandmother who lives in Rochester, New York, recently found herself in danger when an intruder broke into her home. However, instead of leaving with jewelry and money, the criminal left in handcuffs— and with injuries—because he happened to break into the home of an award-winning former bodybuilder.

According to Murphy, she was getting ready for bed Thursday night, after 11 p.m., when she heard a man pounding on her door. “He was outside and saying, ‘Please call an ambulance,’ saying, ‘I’m sick, I’m sick,’” she told WHAM-TV.

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She called the police, refusing to let him inside. Apparently, he got angry and forced his way into her home. “I hear a loud noise,” she said. “I’m thinking, 'What the heck was that? The young man is in my home. He broke the door.”

Instead of allowing herself to be the victim of a crime, Murphy, who works out at the local YMCA almost every day and can lift 225 pounds, fought back.

Because it was dark, she was able to hide while the intruder walked around the house. She grabbed the closest thing she could find—a table— and started attacking him. Once the table broke, she started whacking him with the metal legs.

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“It's kind of semi-dark and I'm alone, and I'm old,” she said, explaining the situation. “But guess what, I'm tough; he picked the wrong house to break into.”

Murphy didn’t stop there. Once he was injured, she ran and grabbed a bottle of shampoo, pouring the entire bottle on him. Then, she finished him off with a broom.

When the officers arrived, the man could barely move, and was sent to the hospital. Murphy believes he was “relieved” to be on his way.

The first responders were quite impressed with her self-defense skills— and rightfully so. “The officers that came wanted to go on my front porch and take selfies with me,” she said.

Murphy, who is not pressing charges, hopes that her story inspires people of all ages.

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Instagram-famous personal trainer (and all-around badass) Kayla Itsines had a baby girl in April—but from the day she announced she was pregnant, Itsines was very vocal about her journey to motherhood and all it entailed (like how she struggled with morning sickness and restless leg syndrome while pregnant.)

Now, Itsines is opening up about one of the more difficult parts of her postpartum journey: Hitting the gym for the first time after her caesarian section—just six weeks after her daughter, Arna Leia Pearce, was born.

Itsines, a lifelong athlete, was eager to get back to working out after she gave birth. She tells Health, “My first session back at the gym, I went onto the treadmill, and I was like, ‘Alright, cool. I’m going to do a fast walk because they told me I could walk.’” 

But that fast walk didn't go entirely as planned. “I stupidly put the treadmill up to a fast walk speed that I used to be able to do. The treadmill started going. I started to feel this weird, odd pain on my right side," she says. "The treadmill pick[ed] up pace quite quickly. I started to panic; I couldn’t turn the treadmill down fast enough.”

Itsines wasn’t able to spread her legs to the sides of the treadmill so she could get off the moving track, and she grew worried she would face plant on the moving belt. Luckily, it slowed down in time for her to regain control, but that incident made her realize just how much her body had changed since she had a baby. That day she ended up walking slow for about 13 minutes. “Then I had to get off,” says Itsines.

RELATED: Kayla Itsines Dishes on Her Fave Foods and More

The realization that she wasn’t as fit as she’d like to be was a tough one. “It was a struggle, really hard. I just remember being so upset and devastated that I wasn’t able to complete [a workout],” says Itsines. That struggle is what led to her new post-pregnancy workout program, to help women who have just given birth figure out how to get back in shape in a safe way. The workouts featured in the program, which include strength-training exercises and low-intensity steady state (LISS) cardio, are 15 to 25 minutes long, and the program lasts 16 weeks.

Itsines says that one thing that made this part of her journey especially difficult was that she didn’t know what it felt like to be out of shape. “It’s different for a person who has, maybe, never worked out before," says Itsines. “For me, I don’t remember not being fit. So I was super confused.”

Itsines stressed the importance of listening to your body when you return to the gym after giving birth, explaining that this is not the time to test your limits. “If I could give advice to women, it’d be not to push them to go straight back into fitness. Not to put that pressure on them…