"And now I can't believe I thought that," she reflects. "Maybe that's what's making me cry is I feel sad for the person who thought he won't be able to locate [us]."
The Manchester By the Sea star is now raising her 11-year-old daughter, Matilda, as a single mom. She admits there have been some challenges.
"It's a little bit difficult to contend with a feeling of failure for not living up to a standard of normal," she shares. "Sometimes it can feel alienating; at school functions, there's only two of us single mothers. Everyone else has a partner, so we buddy up."
Still, Williams isn't looking for a romantic partner anytime soon.
"It's hard to romanticize romance when you're 36," she explains. "When you've been a parent for 11 years and you've done it alone, you don't have romantic ideals, because you have a practical understanding that you can do it by yourself. The romantic idea of meeting your person and having a storybook family life that looks like the model you grew up with -- that doesn't really exist for me."
Williams has dated since Ledger's death, including director Spike Jonze and actor Jason Segel.
"I've not gotten married because I have not had a person to whom I would -- so I have not let my sense of conformity or duty override my instincts," she says.
Of course, Matilda remains her number one priority. "[We're] stuck -- in a good place," she says of their current life. "There's a lot of constancy. She's in such a good place that I don't worry about the stability of our unit when I have to go back to work."
"In all honesty, for pretty much everything else, I feel like I'm a believer in not fighting circumstances, accepting where you are and where you've been. In pretty much all senses but one," Williams told Porter magazine. "I would be able to go totally down that line of thinking were it not for Matilda not having her dad. You know, that's just something that doesn't… I mean, it just won't ever be right."