Rebecca Miller subscribes to the truism “if you want something done right, do it yourself.” Miller writes novels and stories that she adapts into screenplays — and then she directs the movies herself, movies like “Personal Velocity” and “The Private Lives of Pippa Lee.”

Her new movie, “Maggie’s Plan,” stars Greta Gerwig as Maggie, a single young professional who wants a baby, without the bother of a relationship or marriage. But it’s a romantic comedy, so nothing goes as planned. For starters, she meets John, played by Ethan Hawke — a charming, needy, self-centered college teacher and would-be novelist with a wife and kids. John leaves his family for Maggie. But Maggie has second thoughts, and hatches a plan to get John and his ex-wife back together.

Greta Gerwig and Ethan Hawke in “Maggie’s Plan”

(John Pack/Courtesy of Sony Pictures Classics)

Kurt Andersen: All the major characters in “Maggie’s Plan” are deeply flawed human beings, but none of them are villains or awful — is that the mission you began with?

Rebecca Miller: I think most of us exist in the medium-flawed character zone. I don’t think most people are really good, nor are most people evil. That makes them real human beings. I always think that if you present a complex, flawed character that maybe on paper isn’t doing the best things, and an audience can come to love that person, it’s generous to the audience. Because the audience is flawed. We’re all flawed.

I have seen your other four films and in a way it’s the comedy version of those — they’re all about women finding themselves and marriages failing and complicated relationships between parents and children and step children. Was your thought, ‘Ok, I want to do a funny version?’

In some of my movies, for example “The Ballad of Jack and Rose” — nobody would call that a comedy, but there are comical elements to it. When I would be sitting there, listening to the audience, the laughs were really big and surprising to me. And, as time went on, I thought, ‘Well, what if I flipped the ratio and it was more funny than sad?’ Which is actually very natural to me, because I see life in a somewhat absurd comical way.

At one point in the film Ethan Hawke’s character John says, ‘Every marriage has a gardener and a rose.’

I think that in the best relationships you switch on and off. If you have a perpetual gardener, perpetual rose, I think that the gardener will eventually get very pissed off. Unless it’s just a very old-fashioned, kind of masochistic relationship.

As an artist with a spouse — Daniel Day-Lewis — who is also an artist, you must deal with that balance of who’s the rose and who’s the gardener.

Absolutely. You find a rhythm where you’re like, “Ok, it’s your turn now.” There was one time when we made a film together [“The Ballad of Jack and Rose”] and that was sort of tricky, but we managed.

Bonus Track: Listen to Kurt’s extended conversation with Rebecca Miller

Greta Gerwig (left) and Julianne Moore in “Maggie’s Plan”

(John Pack/Courtesy of Sony Pictures Classics)