By DANIELLE GENET and KATIE KINDELAN, ABC News

(NEW YORK) — Joanne P. McCallie, known as “Coach P” on the court, has led her women’s basketball teams through many battles over the past 28 years, most recently as the head coach of Duke University’s women’s basketball team.

Now McCallie, a married mother of two, is opening up about an off-court battle she has faced: Bipolar disorder.

“It was out of the clear blue sky at one of the best times of my life,” McCallie said of the bipolar diagnosis she received at the age of 30. “I struggled early with all the mental assessments and the constant feelings of anxiety and inadequacies. Would I ever be me again?”

Bipolar disorder, or manic-depressive illness, is “a brain disorder that causes unusual shifts in mood, energy, activity levels, and the ability to carry out day-to-day tasks,” according to the National Institute of Mental Health (NIMH).

Nearly 3% of U.S. adults had bipolar disorder in the past year, according to the NIMH.

McCallie, 55, opens up about her own journey with bipolar disorder in her new memoir, Secret Warrior: A Coach & Fighter, On and Off the Court. The book was released Tuesday, more than six months after McCallie stepped away from her 13-year career as the head coach at Duke.

McCallie said revealing her bipolar diagnosis publicly at this time in her life and career was the “only way to do it fairly.”

“It would have been terrible for my teams to bring a huge distraction and to bring it publicly,” she said Wednesday on ABC News’ Good Morning America. “And to be quite frank, I don’t think I was ready. I think it takes some time and maturity to be able to tell your story and to tell it in a heartfelt matter with truth behind it, no denial.”

McCallie, who said she hopes to continue coaching in some capacity in the future, used her experience to take a team approach to treating her bipolar disorder.

“It’s so important for people out there to know that they’re not alone, and speaking from a coach’s perspective, to build your team,” she said. “You’ve got to have a team of people behind you — people that know your truth, that love you for who you are and that can reach out and make a difference in your life.”

“Don’t go alone. Don’t ever try to manage your brain health alone,” McCallie said. “There are so many people out there who can help.”

McCallie, who is also a cancer survivor, said she wants people with bipolar disorder to know the importance of understanding their own brain.

“You have to be honest with yourself. You have to self-analyze,” she said. “You have to understand the power of the brain and do all of the little things — exercise, eat right, get your good sleep — do what you need to do to be in your best health possible.”

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