Wynonna Judd is speaking out about the tragic death of her mother, Naomi. In a preview of a new interview with CBS Sunday Morning, which will air this Sunday, September 25, the 58-year-old opens up about her mother’s battle with depression, which is something Wynonna acknowledges had been an ongoing struggle for her mother for years.

“I did not know that she was at the place she was at when she ended it because she had had episodes before and she got better,” Judd says. “That’s the challenge of mental illness. It’s really, really mysterious. And that’s what I live in, is like, ‘Was there anything I should have looked for or should I have known?’ I didn’t. That’s why it’s such a shock.”

Naomi kept her struggle with mental illness largely hidden from the public eye, due in part to the lack of understanding about what depression really is like.

“People think it’s a character flaw, and they don’t know that it’s this incredibly dark and light experience,” Wynonna shares. “She had incredibly great days in the middle of the dark days. That’s why it’s so confusing.”

Naomi took her life one day before The Judds were inducted into the Country Music Hall of Fame, turning what should have been one of the happiest weekends of Wynonna’s life into an unfathomably heartbreaking one.

“I got the call, and I went over, and I saw her and that was that,” Wynonna recalls. “I said goodbye to her in the hospital, and I closed her eyes, and I kissed her forehead and that was that. And the next thing I know, I’m sitting here on the front porch, on the side porch … you know, and I’m just trying to figure out what’s next.”

After Naomi passed away, Wynonna announced that she would honor the dates that were supposed to be part of The Judds’ farewell The Final Tour.

“I feel her nudging me. And sometimes, I laugh,” Wynonna says. “And sometimes, I say, ‘I really miss you. Why aren’t you here so we can argue?’”

Faith Hill, Trisha Yearwood, Ashley McBryde, Little Big Town and Brandi Carlile are among the artists who will be joining Wynonna on her The Final Tour dates. Martina McBride, who was to serve as the opening act, will also appear on select dates.

“I am humbled, once again, by the loyalty of the fans who have been with us for 38-plus years, who continue to show up for me when I need them the most,” Wynonna said when announcing she would embark on the tour without her mother. “I am grateful that we will continue to honor The Judds legacy, together.”

The Final Tour kicks off on September 30 in Grand Rapids, Michigan. It will conclude on October 29 in Lexington, Kentucky. Find tour dates at TheJudds.com.

If you or someone you know is in crisis, help is available 24/7 from the National Suicide Prevention Line at 800-273-8255.