"One Day at a Time" cast.  Getty Images

The '70s-'80s sitcom "One Day at a Time" was an anthem for a generation grappling with difficult issues never discussed before on television.

Actress Bonnie Franklin was groundbreaking as Ann Romano, a divorced mom raising two daughters. The rebellious older daughter, Julie, was played by Mackenzie Phillips and Valerie Bertinelli played Barbara, the innocent younger sister. Pat Harrington rounded out the clan as the lovable apartment super Schneider, and Richard Masur and Glenn Scarpelli joined in over the years.

The cast reunited for " Good Morning America" earlier this month ahead of the TV Land Awards, which air Sunday at 8 p.m. on TV Land. Just like their characters, the actors have "held on tight" to each other, muddling through, and keeping in touch for nearly 40 years.

When the show was in its prime, millions tuned in to watch TV's first realistic portrayal of a divorced mother struggling to raise her teenage daughters.

"The truth of the matter was…we were reflecting what was out there. It just hadn't been on television before," Franklin said. "You can do all these heavyweight subjects that are important, but you have got to do it with humor."

It all clicked. On TV, the dynamic between Franklin's character Ann and her two daughters was spot on. Behind the scenes, the women say, it was just as natural - though at first, Franklin admits she was skeptical about the castings.

"When they told me Mac [Mackenzie Phillips] was playing my daughter I said, 'That was never going to work…She is too tall'… We met and she had this big mouth as I do, and I thought, 'OK, it's going to be fine'…and then it just was it was easy," Franklin said. "It absolutely happened right away."

"You had one who was sort of the goodie girl, the other the rebel, and the mother who was trying to wrangle them both into some semblance of behavior," Phillips said.

But like the polar opposite sisters they played, Bertinelli and Phillips would venture down two very different paths. For one, it was to teen stardom. For the other, a downward spiral of substance abuse.

"What was going on behind the scenes was certainly more dangerous than what was going in front of the cameras," Phillips said.

Phillips, the daughter of The Mama's & The Papa's lead singer John Phillips, was then 24 and struggling with drug addiction.

"I loved her and I didn't want to see all that pain that she was in," Bertinelli said of her on-screen sister. "Obviously if someone is doing that to themselves they are in a lot of pain."

"My story is no different than any other kid who is going through addiction issues all across the world," Phillips said in the "GMA" interview. "The feelings are the same no matter where the person is."

Phillips' story was more complicated than she would admit for years. The actress revealed for the first time in September 2009 that her rock star father raped her when she was 18, starting a 10-year-long consensual sexual relationship.

Grappling with this and substance abuse while working on "One Day at a Time," Phillips was fired from the show twice.

"Bonnie [Franklin] said, 'We are not going to keep putting money in her pocket to go out and kill herself,'" Phillips recalled.

"She got clean…and then she came back and she was still using again," Franklin said.

Looking back, Phillips recognizes that her co-stars always acted out of love.

"These people loved me until I was able to love myself and when I wasn't able to love myself they still loved me," Phillips said. "They are the kindest group of people you could want."

While Phillips battled her addictions, Bertinelli became a teen sensation.

"Valerie is a testament to what can happen in this industry if you have the proper kind of parenting behind you," Phillips said. "You can survive."

"My job wasn't any more important than my brother's football practice," Bertinelli said. "They were all one and the same."

Now, Bertinelli stars alongside Betty White in "Hot in Cleveland," a TV Land series about the lives of women of a certain age. Her "One Day at a Time" co-stars say they couldn't be prouder.

"Lightning in a bottle is only supposed to happen once…and it happened with this show," Bertinelli said. "This show was huge when it first started in November of '75 and it went through the roof. To have this chance again, at this age, I feel so grateful."

"I love my job and have two hit shows in a lifetime. I am lucky," she said.

"It makes me cry. You made the most of the chance, I mean you did," Phillips said.

And that remains at the heart of "One Day at a Time": making the most of whatever life throws at you.

"I did 20 episodes of this show and people still stop me on the street about it," said Masur, who played Franklin's steady boyfriend in the first season.

"I still get people keep saying the show saved my life," Bertinelli said.