Garner is parent to Violet, 13, Seraphina, 10, and Samuel, 7, with ex-husband Ben Affleck, while Bell shares Lincoln, 6, and Delta, 4, with husband Dax Shepard. The pair spoke to Emilie Haskell, an expectant mom, Deanna Clower, a mom to a 3-month-old infant, and Megan Safar, a mom to two toddlers.
Bell advised Haskell, who was five months pregnant, to stay flexible about labor and delivery.
"Make a birth plan, put a lot of thought into it, take a deep breath and [tear it up]. It's never gonna happen like that, so get rid of it," she said.
Garner and Bell agreed that having children changed them and told Clower to seek support from other moms.
"You're a different self and it's important to talk to other [moms]. Moming is hard, but it's worth it," Bell said.
In addition, Garner and Bell told Safar to ignore her toddlers when they throw a tantrum. Bell shared advice from Shepard, her husband of six years.
"I take the advice of my husband a lot. He says sometimes when they're having a tantrum, treat them like the hot girl in high school. Just ignore them and they'll come to you," Bell said.
"They do like to get you worked up," Garner added.
"I kill the fun. I am so lame. I say no to everything. They call me 'the dragon,' they have all these names for me," she said.