"Had to snag a size large bra and size small pants," the actress wrote on Instagram

Credit: Courtesy Lena Dunham

Lena Dunham turned a minor workout debacle into a major body-positive moment.

The Girls actress-creator shared a mirror selfie after she forgot her gym clothes while paying a visit to fitness guru Tracy Anderson for a Monday sweat session.

“Late to @tracyandersonmethod & forgot my workout clothes so had to snag a size large bra and size small pants (wrong in myriad ways),” the 28-year-old captioned a shot of herself wearing a borrowed black sports bra and some funky printed leggings.

“But do we soldier on? Yes, yes we do because we want to be a strong & happy lady,” she wrote in the post.

Dunham has been dedicated to her new health regimen. And for the star, exercise is much more than looking good.

She shared her newfound fitness philosophy on Instagram last month, writing, “Promised myself I would not let exercise be the first thing to go by the wayside when I got busy with Girls Season 5 and here is why: it has helped with my anxiety in ways I never dreamed possible.”

“It ain’t about the a–, it’s about the brain,” she added.

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Along with celebrities including Jennifer Lopez and Gwyneth Paltrow, Dunham has become a dedicated Tracy Anderson Method convert.

The fitness expert to the stars mixes a high-cardio dance and toning program with a balanced diet (that is not one-size-fits-all) to develop the enviably toned bodies of her loyal clients.

“Have a real conversation about where you’re at with your health. You need to find exercises with some sort of strategy behind them, a strategy for how you want your body to look and perform,” Anderson told PEOPLE before the New Year. “Get real with yourself.”