On her 46th birthday in July, Sharon Horgan shared a video of herself on Instagram. I love being closer to death and an eternity of nothingness, said the Irish writer-actress, grinning incongruously in the clip.

I love watching the people I love get older and decay and die as well. It’s very liberating. So don’t be scared of getting older. Just embrace the horrific awfulness of it.

Horgan’s dark, existential sense of humor will be familiar to anyone who has seen Catastrophe, the biting, not-especially-romantic comedy she co-writes and stars in alongside Rob Delaney. They play a couple whose six-night stand leads to an unplanned pregnancy and a turbulent marriage in the Amazon series, which earned the duo an Emmy nomination for writing this year.

Beginning Sunday, Horgan brings her caustic sensibility to Divorce, an HBO dramedy that chronicles the demise of a decades-long marriage. Created by Horgan, it stars Sarah Jessica Parker in her return to the small screen more than a decade after the women of Sex and the City sipped their last cosmos. While Divorce, set in the New York suburbs, revisits many of the same themes as that landmark series, it strikes a decidedly different tone.

Divorce is a brutally frank portrayal of the resentment and animosity that infect many romantic relationships, even the seemingly happy ones. In a style increasingly common on cable TV and streaming networks (Louie, Transparent, Girls), it consciously blurs the line between laughter and sorrow.

Both sexually and emotionally candid, Divorce is not for the squeamish – though nothing ever is when Horgan is involved.

Like a growing number of female writer-performers, including Tig Notaro, Lena Dunham and Amy Schumer, she mines her life experiences for comedy that is deeply personal and often cringe-inducing in its honesty.

I’m just kind of lucky that I have one of those brains that looks at the (bad) side of things all the time whilst living a lovely life, Horgan says during a trip to Los Angeles this summer. Being a glass-half-empty kind of person and a bit of a pessimist and a loon has totally informed the way I write.

Wearing a decade-old fringed dress by Matthew Williamson (she thinks), Horgan has an unfussy glamour and is blessed with a mane that inspires her producing partner, Clelia Mountford, to call her Sharon With the Good Hair. It’s a combination that could easily prove intimidating, except Horgan, with her potty mouth and throaty laugh, comes off as someone you’d want to split a bottle of wine (or two) with while trading humiliating tales from your 20s.

She has plenty of them. Horgan’s cynicism is hard-won, the byproduct of years spent toiling in thankless day jobs while trying to make it as an actor in London.

A low point arrived right around the time Horgan was turning 30 and working in a Camden head shop.

I thought someone I went to college with was going to see me, someone who thought I was going to do better with my life, and here I am, handing out fliers to come buy a bong, she recalls.

Horgan expresses few regrets about her misspent youth, which she channeled into Pulling, a bleak sitcom she co-created with a friend, playwright Dennis Kelly. In the series, which aired on BBC Three beginning in 2006 and later on Sundance in the U.S. Horgan plays Donna, a bride-to-be who dumps her milquetoast fiance on the eve of her wedding. She moves into a modest flat with two debauched friends – one a hard-drinking schoolteacher, the other a waitress with romantic delusions.

Horgan and Kelly used to describe Pulling (the title is British slang for hooking up) as ‘Sex and the City,’ but with kebabs. But as Horgan notes, Pulling, unlike the consumerist fantasy of Sex and the City, was completely unaspirational. No one would want to be those girls. I didn’t want to be that girl.

As savage as it was filthy, Pulling took a much darker view of the thirtysomething singleton lifestyle. In one notorious scene, Donna discovers that her heartbroken ex-fiance has tried to hang himself. As she tries to free him from the noose, his erection pokes her in the face.

Part of the impetus to create Pulling was Horgan’s frustration with the limited range of comedic roles for women, Kelly recalls. Together, they set out to create a comedy where the women were messy, flawed and allowed to behave like complete reprobates, Kelly says. We decided if anyone was going to be one-dimensional, it was going to be the men. Talk of shoes was strictly forbidden.

‘Pulling’ was like the voice of a generation, recalls Mountford, who runs the London-based production company Merman with Horgan, echoing, perhaps subconsciously, Dunham’s famous line from the pilot episode of Girls. It was the same thing I was doing with my friends, going out there and enjoying life and embracing life and not necessarily tying yourself down to the first man that came along.

Despite a BAFTA nomination and widespread acclaim, Pulling was canceled after two seasons, with little explanation from BBC Three, though Horgan and Kelly have speculated that it was too old for the youth-oriented network. Nevertheless, the series got Horgan noticed by Hollywood. She soon was developing a string of failed pilots for ABC, including an ill-fated Pulling remake. The projects never felt quite like my voice, Horgan says.

Her sensibility was a more natural fit for HBO, where she was commissioned to write a script about two sisters going through hard times – of course, like everything I write, Horgan says, cackling. That project never went anywhere, but Casey Bloys, then the network’s comedy chief, set Horgan up on a work date with Parker, who’d been toying with the idea for a series about a troubled marriage.

Parker, also an executive producer, was excited by the blend of humor and heft in Horgan’s writing. (She) had so much to say about marriage, relationships and being a woman that was completely in line with the story we had been wanting to tell for years, Parker said in an email.

Like seemingly all woman alive at the turn of the millennium, Horgan watched the (heck) out of ‘Sex and the City.’ (Her favorite episode: the one where Carrie repeatedly asks for Aidan’s forgiveness.) As she drafted the Divorce pilot, she did her best not to dwell on the fact that she was writing for Parker, one of the most famous women in the world.

If I did, my brain would explode, she says.

The pilot is vintage Horgan: Parker’s character, Frances, is moved to break up with her husband, Robert (Thomas Haden Church), at a party thrown by a couple consumed by near-homicidal resentment of each other. In response to the news, he vomits. (A virtually identical scenario plays out in the pilot for Pulling.)

I think it would be very easy to tell this story if it was just dramatic, says Horgan, who looked to the Kathleen Turner-Michael Douglas black comedy The War of the Roses as a model. By making Divorce a comedy, she and show runner Paul Simms (a former writer-producer on Girls) aimed to take viewers on a roller-coaster ride where they’re laughing one minute and hopefully shot in the heart the next.

Divorce came together virtually at the same time as Catastrophe, which Delaney and Horgan wrote after striking up a friendship on Twitter. The story of a fling that unexpectedly morphs into a permanent commitment was partially drawn from Horgan’s life: She found out she was pregnant after dating her now-husband, Jeremy Rainbird, for only six months (they’ve been married for more than a decade and have two daughters).

The series, which debuted on Amazon last year, provides an unflinching look at the difficulties of juggling marriage and parenthood, even for two people seemingly meant to be together. There are story lines around forgotten breast pumps, pre-cancerous growths and dead pets.

Whatever organ squeezes out art juice, hers is very, very healthy, says Delaney, an American standup who, before Catastrophe, was best known for his wickedly funny Twitter feed. She understands that there is no light without dark.

After numerous professional false starts, Horgan is now in the nutty situation of having two shows she created premiere within 18 months of each other, a hot streak she attributes to a growing appreciation for female-driven storytelling.

And there’s more to come from Horgan, who recently produced and co-wrote two pilots for the U.K.’s Channel 4: The Circuit, about a nightmarishly uncomfortable dinner party, and Motherland, an acerbic take on middle-class moms.

She has also committed to at least two additional seasons of Catastrophe, and with Mountford is developing a range of projects. At some point, she hopes to do some acting outside of Catastrophe, because, as she puts it, it’s fantastic to be someone else, and writing is a pain in the hole, though so far there are no plans for her to appear in Divorce.

Getting her first big career break at age 36 – positively geriatric by show-biz standards – has inspired Horgan’s frenzied work pace. She admits feeling a bit panicky if she doesn’t have a project lined up – an increasingly rare circumstance these days.

I may as well be using this washing machine that is my brain, she says. Otherwise, it’s just a load of voices.