Kathryn's inability to be careful with other people is central to the series, which tackles the joys — and strains — of long-term friendships.
"The show, to me, is a lot about female relationships," Garner said. "And it's a lot about just friendship over time and what friendships can go through and still be richer for it. Or what the breaking point of a friendship might actually be."
Garner said her own decades-long bonds with friends made the series ring especially true.
"I haven't had many friendships break, thank goodness, but I have had friendships endure. I can look at several girlfriends and say, 'Yes. This has been one of the dearest people in my life for 20-plus years,'" she said. "And that takes something. I can think of a time where I was selfish and injured a friendship. And it took years and years, but now, that's just a blip in the past."