The 26-year-old actress -- who gave birth to her 1-year-old daughter, Kaya, in December 2014 -- says she was scared that people were going to judge her for the decision in a candid new interview with Yahoo Style.
"I was always so terrified that people weren't going to accept me," Panettiere confesses. "I finally just went, 'I'm tired of living afraid. I'm tired of living in fear of what people are going to think, so, you know, I'm just going to put it all out there on the table and I'm not going to worry about the judgment.'"
"The more open I was, the more acceptance I got from people," she continues. "I got so much support and so much love. I was floored. I feel much more exposed, yes, but in a great way."
And Panettiere has a message for those doubting the existence of the condition.
"If you think for one second that a mother wants to feel that way toward her child, you're outta your mind," she says bluntly. "It is one of the most debilitating, scary, guilty feelings that you can ever feel. That a mother would not be able to connect with their child, would not be able to get a grip, or would not know what's going on, for anybody to say that it's false or created by us, you must have your head examined."
The actress admits it's been hard returning to her work on Nashville, because her character, Juliette, is also struggling from postpartum depression -- a story arc that she says was actually coincidental.
"It was strange having to throw myself back into that frame of mind," Panettiere shares. "The way I do things is to pull from my own personal experience, and sometimes even turn myself into what I'm portraying, so that I can pull from my life and step into that person's shoes by being able to relate."
These days, Panettiere says she's not so worried about constantly holding on to her "good girl" image in Hollywood.
"I grew up with the Lindsay Lohans and the Paris Hiltons," she explains. "I was in the same generation. I was expected to do the exact same thing. I was watched like a hawk to not fall into the same groove, and I fought against that for so long."
"People connect with being human, with being real, with just doing your own thing," she now reflects. "That confidence in doing your own thing is something that I'm learning more and more and more about, and it feels good. It feels really good."
This past Saturday, Panettiere shared a few super sweet photos of her and her fiance, 39-year-old boxer Wladimir Klitschko, with their adorable baby girl.
"The loves of my life," she captioned one sweet photo of the father-daughter duo playing on the beach.
When ET chatted with Panettiere at the Critics' Choice Awards in January, the actress said she was surprised by all the positive reaction she got after opening up about her own experience with postpartum depression.
"I've gotten an incredible amount of support, and I was actually really surprised because I feel like I grew up in this industry that, in my mind, was very judgmental," she said. "I didn't even look at social media. Then, when I looked, people were like, 'Oh my gosh, good for you,' and I am so proud to be a spokesperson and a woman that people can look to, and to know that they're not alone and they're not weak if they go and they seek help."