"I just kept putting it off," Retta tells PEOPLE

Retta was once invited to audition for the role of Effie White in the 2006 film adaptation of Dreamgirls — but she didn’t end up participating in the casting process at all.

The former Parks and Recreation actress, 48, opens up about the experience in the latest episode of The Jess Cagle Interview, explaining that her decision not to audition stemmed from her “fear of success.”

“I just kept putting it off,” she admits. “I was so scared — because I have a bad knee, I have a bad ankle, so I can’t wear heels, and I knew they were going to want me to wear heels. I was like, ‘How am I going to fake it for a whole shoot?’ And it’s a girl group, so they have to be dressed alike, and I didn’t know how they were going to dress us alike.”

“There’s no way they were going to have something in my size that they’re going to have in their size, or something that they have in the other girls’ size that they’re going to find in my size — not knowing that costume departments make the clothes,” she adds. “I legit thought they were going to Nordstrom!”

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The role ended up going to Jennifer Hudson, who took home the Oscar for best supporting actress. Asked what held her back, Retta says she was “afraid of being the problem on set.”

“I was afraid they were going to think I was a diva, when it was just my fears of my knees and the shoes and I know how I am when I’m uncomfortable in clothing,” she says. “I was afraid they were going to see me as this person, like, ‘Why are you causing so many issues when you’re the newbie?’ ”

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Looking back, the actress admits she threw up her own roadblocks.

“I sure did. That’s when I learned the … I never understood the phrase ‘the fear of success,’ ” she says. “I was like, that’s the dumbest thing I’ve ever heard. And it was in that situation, where there was a situation where I could be successful, and I was scared. I was scared of what it was going to take to actually get to the end point of it.”

Retta’s memoir So Close to Being the Sh*t, Y’all Don’t Even Know is on sale now.