Miranda, who shed 20 pounds from her 5-foot-4-inch frame last year and has since kept the weight off, tells the magazine that a big motivation is performing for her thousands of fans.
"When you have to walk out there in front of thousands of people, it does feel good to know that your s--t’s not jiggling," she says bluntly. "I'm just like anybody else, insecure and scared of looking bad or being criticized."
Though, Miranda hates the media's fascination with her noticeable weight loss.
" ... Everybody's making this big, giant thing about it," she says. "It's way too much focus on women's bikini photos, and I hate it. Why do we care? I want women to love themselves whatever they've got going on."
But despite her healthier eating habits since turning 30 last year, Miranda does admit to still indulging in alcohol.
"I'm not afraid of a pill," she jokes. "I have to take them in the mornings because I drink a lot. Advil helps. So does a Bloody Mary."
But on a more serious note, Miranda also reveals that she struggles with feeling anxious on a day-to-day basis.
"I will worry myself into oblivion," she shares. "[But] I learned everything doesn't have to be perfect. That sometimes it's OK to say, 'I don't want to be the boss today. I have PMS. Bother someone else.' I like things better flawed anyway."
And her moods sometimes extend to her marriage to "The Voice's" Blake Shelton.
"I'm not sunshine and roses," she says. "Blake's the happiest person on the planet. He pulls me out of my darkness … Literally, everything is the best about being married."