Mariel Hemingway: 'I Was Afraid That I Was Going To Wake Up One Day And Be Crazy' (VIDEO)

Mariel Hemingway, the model, actress and granddaughter of legendary novelist Ernest Hemingway, comes from a family plagued by mental illness. Seven members of Mariel's family have taken their own lives, including her famous grandfather and her sister, Margaux. In this clip from "Super Soul Sunday" on OWN, Mariel, an outspoken advocate for mental health, opens up about her fear of following in her family members' footsteps.

"I was afraid that I was going to wake up one day and be crazy," Mariel says. "I really thought it's in my blood. Everybody says it's genetic, and so you worry."

Sitting next to her partner, Bobby Williams, Mariel tells Oprah that she's chosen to live a mindful life. "You have to be very conscious and aware. You can't just put it on cruise control. You have to be conscious every moment," she says in the video.

"When I live that way, and it's my choice and it's my joy, then I know I overcome anything. Any obstacle," she says. "But it took me to have to go through it. It took me to be afraid."

"Because you were afraid you were going to end up like that," Oprah says, referring to Mariel's family members.

"Oh yeah," Mariel says. "When my sister killed herself, I actually thought, 'Oh, no.' I thought it was like the baton being passed to me. It's my turn."

"Wow," Oprah says.

"She's gone. Now it's going to be my turn," Mariel says. "And here's the horrible thing about worrying you're going to go crazy, is you're not going to know you're crazy. You're just going to wake up and be in a hospital. You won't even know you're there."

Oprah's conversation with Mariel on "Super Soul Sunday" airs Sunday, September 22 at 11 a.m. ET on OWN. Her autobiographical documentary, "Running From Crazy" will air on OWN in early 2014.