Jennifer Garner stars in upcoming comedy, "Yes Day," a film based on a tradition she's been doing with her kids for several years now.

The actress and mom of three, 48, has long been a fan of the annual day in which parents say "yes" to their children's requests for 24 hours. She first learned about the idea from a children's book, "Yes Day!" by Amy Krouse Rosenthal, which the Netflix film is based on.

In Garner's family, she says she sets up a few "ground rules" before the big day.

"You can't get anything in the future, you can't pierce your ears, get a dog -- things like that because, of course, that would be the go-to," she explained during an appearance on "Good Morning America" Tuesday. "And then I always have my own personal rule that you can't eat so much junk that you feel sick because that ruins the day, which is kind of a downer because it's a lot about eating."

Garner emphasized that the day is really intended to be just a fun day spent together with your children -- and the focus isn't about spending money. She also shared why the lighthearted film based on the "Yes Day" idea is a "breath of fresh air" during this time.

"It is all about just saying yes to your family, saying yes to time together, yes to yourselves as moms," she said about the film. "We lose ourselves ... you can kind of feel rigid because you're just trying to keep everyone on track."

"Get the right lunch and the right lunch box and people to soccer, ballet or on Zoom for school -- whatever it is -- and so you just find yourself say 'nope, nope, nope' without even thinking about it," she said. "Letting go of all that for a day is really liberating ... it's a beautiful family tradition. But, of course, because I have a teenager, this movie also really addresses the yeses that come with letting your kids grow up."

Garner also discussed reuniting with her "13 Going on 30" co-star Mark Ruffalo in another upcoming film, "The Adam Project."

"It was wonderful," she said on working with Ruffalo again. "We were playing a married couple and we just had this instant comfort and obviously there's just such a connection and a warmth. It was actually a really beautiful experience to revisit that relationship."

She also had a chance to recently see another one of her co-stars from the film, Judy Greer. "We saw each other right before I saw Mark, so I was able to kind of pass messages back and forth," she said. "It was really fun."

When asked what her famous character Jenna Rink would be up to now, Garner said she hopes she would "still be whimsical and have a little bit of fun."

"She would have to still have some 13-year-old in her," she said with a laugh. "But, oh, gosh, I have to go back and watch this movie. It's so fun ... Is Poise still going? Is it all online? What's happening?"