Life’s been hard on Diane: A widow with a drug-addicted son and ailing friends, she seems to take care of everyone but herself. Opening Friday, the film “Diane” would be a real downer if not for Mary Kay Place, who plays her. The spunky blonde of such ’70s and ’80s classics as “Mary Hartman, Mary Hartman” on TV, and “The Big Chill” dominates every frame of Kent Jones’ drama, although it’s hard to recognize her at first under a mousy brown wig and harsh black eyeliner.

“I’ve met versions of Diane,” the 71-year-old Place tells The Post in her native Tulsa twang, untouched by decades in Los Angeles. “Women who lived to serve, but didn’t know what their own needs were . . .” She laughs, adding, “The patriarchy has been in charge way too long!”

A former recording artist and TV writer (“The Mary Tyler Moore Show,” “M*A*S*H”), Place talks about cutting loose, staying single and the warmth she feels for her “Big Chill” co-stars.

“Diane” is intense. Where was it filmed, and how did you decompress?
We shot it in 20 days in January in Kingston, NY. The days were long, and I’d come back to the Airbnb I was staying in and dance like crazy in the living room. I made a “Diane” playlist — Leon Russell’s “Out in the Woods” is on it. I can really go to town on that one! I also did mindful meditation. There are free, guided audios that can help calm the central nervous system and lower the heart rate. As Jessica Lange said in some article, “Your body doesn’t know you’re acting!” It puts your system through stress, so you have to counter that.

You’ve played so many mothers; you’ve neither married, nor had children. Any particular reason?
I think in my past lifetime, I had six children and a needy husband. I wanted a creative life, to stand on my own two feet and not be beholden to a marriage or a man to support me. That’s not to say I don’t have incredible relationships with men, but I never felt I met my true mate. And “The Big Chill” was very helpful. I had friends who, like my character, knew they wanted a child. After that movie, I felt it was OK if I didn’t.

How tough was it acting and writing in the pre #MeToo ’70s?
People were nuts then. They had too much to drink, they were doing drugs, they might have made passes or done stuff they shouldn’t have. But I never felt I was in danger. I grew up with two brothers and we tortured each other, so I was pretty tough. But you can’t get away with that s - - t anymore!

Your “Big Chill” co-stars included Glenn Close, Kevin Kline and Jeff Goldblum. How much fun was that?
We had an absolute, total, complete blast! Everything was set up so we could have that connected feeling. We danced our guts out and played Trivial Pursuit and charades every night. That’s why my eyes look so tired. I don’t know how we had the energy to do that. Oh right, we were young! I’m still good friends with Glennie and Kevin. I don’t see Jeff so much because he’s got two kids.

Still in touch with “Mary Hartman” star Louise Lasser?
I talk to her periodically. I saw her on “Girls” and thought she was brilliant! “Mary Hartman” was a wild time, too. We did five, 30-minute episodes every week and wore ourselves to a nub! When we were good, we were really good, and when we were bad . . . [laughs]

You recorded three country-pop albums. Still performing?
I’m perfectly happy singing all by myself in the kitchen. I think it’s good for the soul. That’s how weird I am!