The author of Strong Looks Better Naked, who frequently documents her early morning sweat sessions and spin classes, has lost around 40 lbs. since adopting a take-no-prisoners attitude to the gym and her diet.
"I definitely think the physical and the mental go hand in hand," Kardashian tells PEOPLE exclusively. "I feel so good in the gym that it [affects] the rest of my day. It's a healthy addiction. It's like buying your sanity!"
But when Kardashian's entire world was thrown for a loop following the tragic overdose and hospitalization of her estranged husband Lamar Odom, the reality star had to find another outlet for peace of mind.
"Mentally, it took its toll on me," says Kardashian, who didn't leave Odom's hospital room for weeks. "But for the first month, I wasn't even really thinking about that. It wasn't about me. But once I started getting my feet back under me a little bit, I was like, oh my God, I need to get back to my routine."
RELATED VIDEO: Khloé Kardashian Shares Cryptic Instagram After Lamar Odom Leaves Hospital
Returning to the gym after a six-week hiatus was tough for Kardashian. "My stamina was affected," she says.
"I do these drills where I'm running and I realized how out of breath I was compared to how I normally was. But I worked so hard to get there, I couldn't lose it."
Now that her life is somewhat back to normal (Odom continues to recover and entered a rehab facility this month), Kardashian, who has a new show, Kocktails with Khloé, is steadfast: four days a week in the gym with trainer Gunnar Peterson and a fresh diet (more on that here).
"I want whatever is quick, so having healthy items available when I'm hungry, there's no excuse," says the former junk food devotee who now snacks on fresh fruit and pre-cut up veggies from her stocked fridge and keeps the treats like pizza and candy to a minimum. Still, "I don't deprive myself," says Kardashian. "I'll still have a piece of cake; I just won't have two of them!"
Kocktails with Khloé premieres Jan. 20 at 10 p.m. ET on FYI.