Motherhood changes everything. One day you’re debating Kosovo, the Knicks and the Tonys. The next you’re discussing the quality and quantity of . . . poop.

Indeed, the day you take your first baby home, it’s like the final scene in ‘The Graduate,” when Dustin Hoffman and his freshly captured bride jump on the bus. They made it! Now what?

Now what, indeed? For most of us, it’s chaos and spilt milk, sleep deprivation and diapers, and a lifetime legacy of guilt.

It’s also gummy smiles and sticky kisses, papier-mache jewelry and a fierce, frantic love like nothing we’ve ever known before.

And none of it comes easy.

MAKING MISTAKES

No matter who you are – a waitress, a rocket scientist or the First Lady – nothing makes you feel as incompetent as your first child.

‘I remember when I was breast-feeding Chelsea when I was still in the hospital,” Hillary Rodham Clinton once said. ‘I had her head tilted at a funny angle and the milk started to come out of her nose. I thought I was killing my baby . . . ” A nurse came to her rescue.

No one has written more frankly about feeling incompetent than Anne LaMott. In ‘Operating Instructions: A Journal of My Son’s First Year,” the writer and single mom chronicled every stumbling block in the road, from his colic to her fear she was raising an ax murderer.

But Sam LaMott, now 9, seems to be doing fine.

‘I decided at some point, early on, that I’d let myself make every mistake in the book – and I have,” she says, ruefully.

Judith Viorst, whose sons Nicholas, Anthony and Alexander are long grown but remain young in her children’s books, including ‘Alexander and the Terrible, Horrible, No Good, Very Bad Day,” still remembers what it felt like to clip her baby’s fingernails and draw a single drop of blood.

‘I cried for two hours,” she says. ‘I thought there’d be a knock at the door and someone would arrive saying, ‘You obviously aren’t equipped to have a child.’ ”

Fortunately, babies are more resilient than you think . . . and mothers are innately more competent than they believe. As Dr. Spock put it in his ground-breaking ‘Baby and Child Care”:

‘Trust yourself. You know more than you think you do.”

FRIGHTENING FEELINGS

The baby won’t sleep, which means you can’t sleep either. Or she’s just thrown her binky across the room for the 500th time and you refuse to pick it up. At moments like these, ‘maternal” is about the last thing you feel. You may in fact be feeling a wild, unreasoning hatred that terrifies you. But that’s perfectly normal, the experts say.

‘Anger is the part of motherhood no one wants to acknowledge,” says Sandi Kahn Shelton, author of ‘Sleeping Through the Night . . . and Other Lies.”

‘But it’s there, and if you try to subvert it, bury it, it only feels worse.”

She recalled how she’d felt when her three children were young and she was, for a time, the only parent in the house.

‘I remember thinking I’d tear my hair out and theirs as well. So I’d sing a little song, ‘You’re making me crazy, you’re making me crazy,’ and they’d join in. That took the edge off.”

A 35-year-old mother, who wishes to remain anonymous, admits she once dropped off her 4-year-old at daycare stark screaming naked. (He was naked; she was screaming.) He’d resisted everything she tried to dress him in; at last, desperately late, she tossed him, his underwear and the rest of his clothes at his teacher and fled.

‘I tell people this story and explain that this was my low point as a mother,” she says. ‘Fortunately, the teacher was great.”

It helps to laugh. And if you can’t laugh, well . . . share your frustration with a friend.

‘You need people you can call up and say, ‘I really think I’m going to lose it with this kid,’ ” Shelton says. ‘Anyone who has any decency at all will assure you that they’ve felt the same way.”

When her patience fails her, LaMott – also the author of ‘Traveling Mercies: Some Thoughts on Faith” – turns to prayer.

‘I give myself timeouts,” she says. ‘I stop myself and pray. ‘Please help me know what to do next.’ And the next operating instructions come.”

She and her son Sam also have a rule: ‘You’re allowed to be mad, but you’re not allowed to be mean. That helps us a lot.”

GETTING RID OF GUILT

As any expert on free association can tell you, the word most frequently associated with motherhood is . . . guilt.

The baby falls and scrapes his knee and we feel guilty that we weren’t there padding the ground for him. Our teen-ager doesn’t make cheerleader, and we feel . . . if only we’d practiced those cheers with her more.

Sometimes, even the good things we do are loaded with . . . guilt. When Sanjean Scanplebury left Barbados to make her way in Brooklyn, she had a lot of settling in to do. So she sent her young daughter home to the Caribbean island with a relative while making her way.

‘We were apart only three months, but it felt like eternity,” she says now. ‘I missed her first steps. I’m still trying to make up for it!”

According to Long Island psychologist Jean Cirillo, guilt comes with the territory.

‘Mothers are programmed to feel guilt whenever anything goes wrong with their child, whenever their child feels any pain,” says Cirillo. ‘I’ve heard someone say, ‘A mother is only as happy as her least happy child.’

‘But part of the human condition involves some suffering,” she adds. ‘Why should your children escape when no one else has?”

Still, Cirillo says, there is an answer, a way to squelch (at least somewhat) that eternal flame of maternal guilt.

‘Kids rebound better than you think,” she says. ‘Their egos are stronger than you’d think. And once they’re recovered, they get upset that you’re upset.

‘You have to have what we call ‘detachment with love.’ You love your child, you want the best for her, but if she hurts, you only hurt down to a certain point . . . you’re able to detach enough so you don’t blame yourself every time something goes wrong.

Adds Shelton, whose children now range from 10 to 23: ‘One thing I’ve learned is that you can get rid of the guilt a little bit if you make clear to your children that you’re there for them, but you can’t necessarily solve their problems or even take responsibility for them. Instead, you’re their companion, the one they can vent to.”

COMPARING KIDS

Fondly, you watch your 4-month-old bat aimlessly at his Sesame Street play gym. Then Baby Natalie comes to visit. She’s the same age as your little Nathan, but when she gets under the play gym, she seizes one of its figures in her perfect fist and brings it close to her eyes, as if she’s reading the inscription ‘Made in Japan.” Suddenly, your marvelous son doesn’t seem so . . . marvelous anymore.

Face it: comparing children is hideous – especially when it’s your child who falls short.

LaMott remembers how her son was so late in speaking that she tried to convince herself that his incoherent wails were actually Latvian.

‘This sounds so Pollyanna-ish,” Shelton concedes, ‘but try to see what it is in your child that you value. If your kid has this gentle soul and wonderful way with people, that’s what you nurture and fasten onto. And many children do have that – you just have to see it and encourage it.”

Also forget about playing Pygmalion, she says. There’s a limit to how much you can mold a child.

‘We have the idea that if we put the right ingredients in, it will all turn out a certain way,” she says. ‘But we don’t have that control at all. Children are born with their own personalities, and our amount of interest is more limited than we’d like to think. What they mostly need is our approval for who it is they are, rather than our trying to mold them into what we want them to be.”

ASKING FOR ASSISTANCE

Motherhood, the experts agree, has gotten harder lately. Mostly because our expectations – and everyone else’s – have raised the stakes. Whether you’re a working mother or a mother whose work is in the home, you’re still probably having a tougher time of it than your own mother did.

‘I think society today is more critical of mothers,” Shelton says. ‘When a 2-year-old used to freak out in public, everyone used to just shake their heads, and say, ‘Oh, that’s toddlers.’ Now I see moms out there who, when their kids start to cry, get these panic-stricken looks on their faces. They’re afraid everyone thinks it’s their fault – that it’s child abuse.”

The best thing you can give a mother is support, approval . . . or simply another pair of loving arms.

Shelton recalls the time she and her husband had taken the baby to a restaurant, but the food was slow in getting there, and even before it arrived, the baby was screaming in his clip-on seat.

The waitress appeared.

‘Here,” she said, soothingly. ‘Let me take him.” She lifted him out and carried him around the restaurant until he cooed while the rest of the family enjoyed their meal in peace.

‘We can’t do this alone,” Shelton says. ‘No mother animal is alone with her baby 24 hours a day, seven days a week. The other members of the animal kingdom put them in safe places and take a break. Humans don’t get to do that so much.”

You can if you ask. And Anne LaMott firmly believes in asking for help.

‘I couldn’t do it alone,” she says. ‘You need a chosen family, people who will be the pit crew for your child. You can call them up and say, ‘This really isn’t going well today. I’m at the end of my rope,’ and they’ll say, ‘OK. Why don’t you bring him over?’ But of course your child doesn’t act like Ivan the Terrible at their house – just in yours – so it’s all right.”

REAPING THE REWARDS

‘I always have to struggle to overcome a prejudice I have that people without children can’t imagine what they’re missing,” says Viorst, author most recently of ‘You’re Officially a Grownup: the Graduate’s Guide to Freedom, Responsibility, Happiness and Personal Hygiene.”

‘My father once said that my three sons were the best work I’ve ever produced. Certainly nothing else has given me this much satisfaction.” And most moms would agree.