For 25 years on her hit talk show, Oprah Winfrey shared valuable wisdom to inspire personal growth and help others navigate their bumpy lives.

But where did Winfrey turn for her own self-help?

“I’ve never been to a therapist because I had so many on the show, but my real therapy came from downloading whatever was happening in the day with Gayle every night,” she tells PEOPLE in an interview for the magazine’s 50th anniversary special issue.

Gayle, of course, is Gayle King, Winfrey’s BFF for nearly half a century.

“There wasn’t a day that we missed being on some kind of phone call talking about what had happened in our days,” she says of their bond that dates back to WJZ-TV in Baltimore when Winfrey was a 22-year-old news anchor and King a 21-year-old production assistant/writer at the station.

The powerhouse duo have become a force of nature over the decades. Fiercely loyal and always truthful with each other (“even if you don’t want to hear it”, Winfrey told PEOPLE in 2022), they share similar values and philosophies about life and relish a good meal, a great movie and a spirited discussion around current events.

And that nightly check-in.

“I realized years later, talking to an expert about something else, that that was my therapy, that was my release,” she says.

“That was the way I not only kept myself grounded, but it was the way I regulated myself every day.”

Winfrey, 70, remains forever grateful for King’s guidance and ongoing mutual support. “I’ve had one of the best friendships anybody could have,” she says. “And you can only do that when somebody cares as much about your success, your sadnesses, your triumphs as you do.”

Along with King, Winfrey credits her late friends Maya Angelou and Sidney Poitier for helping her navigate life over many years.

She says: “Those were the people who kept me grounded.”