Michelle Obama reflects on being the first black first lady and her reaction to Donald Trump winning the presidency

In her new memoir, former first lady Michelle Obama reveals the extraordinary highs and devastating lows that marked her journey from a working-class neighborhood in Chicago to the White House.

"Becoming" is an in-depth, personal look at Obama's life -- both inside and out of the White House -- and she opened up about it all to "Good Morning America" anchor Robin Roberts in an ABC News primetime special before the book's release on Tuesday.

For the first time, the former first lady spoke publicly about deeply personal issues, including her past fertility and marital struggles, her profound anger at President Donald Trump, and the bigotry and hate she encountered on the campaign trail.

She also revealed what she calls a "painful secret" -- that she didn’t believe her husband could be elected president.

And through it all, this star student who went to Princeton and Harvard, then became a successful lawyer and executive while raising two young children, then went on to become the first lady of the United States, says she was always asking herself -- "Am I good enough?"

"Being the first black anything is gonna be hard," she told Robin Roberts. "I knew, as the first black first lady, I couldn't presume anything ... I'd have to earn my grace."

(MORE: TRANSCRIPT: 'GMA' co-anchor Robin Roberts interviews former first lady Michelle Obama)

Changing the face of the White House

Known as a fashion icon with a common touch, the self-proclaimed "mom-in-chief" ushered in a modern era to the White House. She championed "fitness challenges” and vegetable gardens, brought diversity to the forefront, and had fun dancing along the way.

She credits her father Fraser Robinson with teaching her the dignity of work and hard-earned money and her mother, Marian Robinson, who lived at the White House as the "first grandmother," for helping her balance the demands of raising a private family in a very public house.

“My parents, from a very early age, encouraged us to put our opinions on the table, to ask questions, to question the context of situations,” she told Roberts. “You could speak your mind, but you had to be respectful, you know? And if you got outta hand ... you'd get a spanking.”

(MORE: Michelle Obama's inspiring message to first-generation college students: 'There are so many people who believe in you')

Lust, love and working together on their marriage

In the book, Obama describes how her initial attraction to her now-husband, Barack Obama, whom she met as his mentor at the law firm Sidley Austin LLP in Chicago, blossomed into romance when they stopped for ice cream one summer night.

“He played it real smooth," Obama told Roberts. “He just leaned in for a kiss. And that really was it. You know, from that kiss on ... it was love. And he was my man."

(MORE: Michelle Obama surprises a dance class at her former high school and it's amazing)

Despite the immediate attraction at first, she had insisted that they should just be friends, but writes in the book: "As soon as I allowed myself to feel anything for Barack, the feelings came rushing – a toppling blast of lust, gratitude, fulfillment and wonder."

When Roberts remarked that you wouldn’t normally hear the word "lust" from a first lady, Obama shrugged and smiled.

"I don’t know what to tell you,” she said. “It was there. It still is. I love my husband a lot."

Journey to motherhood and the pain of miscarriage: 'I felt like I failed'

Obama also reveals some of the serious challenges the couple confronted in their relationship.

First, her struggle with infertility.

"It turns out that even two committed go-getters with a deep love and robust work ethic can’t will themselves into being pregnant," she writes in the memoir.

When she eventually did become pregnant, she miscarried weeks later.

"I felt lost and alone," she told Roberts. "I felt like I failed because I didn't know how common miscarriages were because we don't talk about them. ...We sit in our own pain, thinking that somehow we’re broken."

She revealed to Roberts that she underwent in-vitro fertilization (IVF) to conceive her two daughters, Malia and Sasha.

"The one thing I wish somebody had told me about getting pregnant is that it's not that easy all the time," she confided to Roberts. "I think it's the worst thing that we do to each other as women, not share the truth about our bodies and how they work and how they don't work."

Obama also talked about a time when the stress of their hectic schedules threatened to overwhelm their relationship and the couple sought marriage counseling.

"I know too many young couples who struggle and think that somehow -- there's something wrong with them,” she said. “And I want them to know that Michelle and Barack Obama, who have a phenomenal marriage and who love each other, we work on our marriage. And we get help with our marriage when we need it.”

Michelle Obama on the bruising campaign to the White House

When her husband, then Illinois Senator Barack Obama, started talking about running for president in 2006, Obama said her reactions were mixed. While she believed he would make a great president, she also worried about what it would do to their family and their marriage.

She reluctantly gave him her blessing to run but admits in the book she was "at the same time harboring a painful thought: Barack was a black man in America, after all. I didn’t really think he could win."

Even so, Obama threw herself into the campaign, often catching early morning flights and making three or four campaign stops a day. As her popularity increased, so did the personal attacks.

“People called me Barack's baby mama,” she told Roberts. “Accused me of not loving my country. You know, told me I was angry.

"It was the first time I really experienced someone taking my voice and ballin' it up and distorting it," she recalled. "And in a way, I was, like, 'This isn't me. Wait, wait, people. This isn't who I am.'"

In her memoir, she write, "this stuff hurts."

And the hurt would continue straight into the White House. She writes in her memoir how Trump and other so-called "birthers" in 2011 began to openly criticize whether her husband was an American citizen, questioning his legitimacy.

She writes, "I feared the reaction. What if someone with an unstable mind loaded a gun and drove to Washington? What if that person went looking for our girls?" "Donald Trump, with his loud and reckless innuendos, was putting my family's safety at risk. And for this, I’d never forgive him."

And when the now infamous "Access Hollywood" tape with Trump surfaced weeks before the presidential election in 2016, Obama writes that she "channeled my fury into words" and delivered a scathing rebuke in a campaign speech from New Hampshire.

"This is not normal. This is not politics as usual. This is disgraceful. It is intolerable,” she said in that speech.

"My body buzzed with fury after hearing the tape. I articulated my rage and my fear, along with my faith that with this election Americans understood the true nature of what they were choosing between,” she writes.

She continues: "We were now up against a bully ... challenging the dignity of our country with practically his every utterance."

How Michelle Obama reacted to Donald Trump winning the presidency

On election night, when it became clear Trump might be the next president of the United States, Obama says she wanted “to block it all out and go to sleep.”

She writes: "I will always wonder about what led so many women, in particular, to reject an exceptionally qualified female candidate and instead choose a misogynist as their president."

She describes coming to terms with the new reality. As the nation watched the peaceful transition of power from President Obama to President Trump on January 20, 2017, she writes that "the vibrant diversity of the two previous inaugurations was gone ... Someone from Barack's administration might have said that the optics there were bad -- that what the public saw didn’t reflect the president’s reality or ideals. But in this case, maybe it did. Realizing it, I made my own optic adjustment: I stopped even trying to smile."

In the ABC News interview, Obama said simply: "Being the commander in chief is a hard job. And you need to have discipline and you need to read and you need to be knowledgeable. You need to know history, you need to be careful with your words. But voters make those decisions. And once the voters have spoken, you know, we live with what we live with."

When pressed by Roberts if the “seeds of discontent that led to Donald Trump being elected president” were planted during her husband’s presidency, Obama said she couldn’t get into the minds of the voters. "We’re gonna have to figure that out as a nation," she said.

When Roberts asked how the current first lady, Melania Trump, is doing in terms of defining her role, Obama said she has decided not to judge those who come after her.

"I think every first lady approaches this job differently," Obama responded.

She did, however, say that Mrs. Trump had not reached out to her for advice.

Empowering girls and women around the world

Beyond the White House, Michelle Obama continues to advocate for women and girls in the U.S. and around the world. Her daughters, who came into the White House as little girls, are now accomplished young women.

Sasha, 17, will graduate from high school this spring, and Malia, 20, is a sophomore at Harvard.

“This is one of the greatest lessons that my mother taught me is that children -- you aren't raisin' babies,” she told Roberts. “They're only gonna be cute and little for a little while. But then they grow up and they have to be adults in the world. And everything we do as a parent with our children, we're preparing them for adulthood.”

Obama continues to support initiatives that empower adolescent girls to get an education -- such as "Let Girls Learn" and "Global Girls Alliance." The Obama Foundation Scholars Program is also bringing young leaders from around the world to study in the U.S.

Their first assignment: learning about the South Side of Chicago, where it all began.

In writing her book -- sharing all the successes and difficult moments -- Obama said she hopes she can inspire the next generation to become whoever they aspire to be.

“I think that young people are the future,” she told Roberts. “And if my story, my journey somehow gives them hope -- that they can build a powerful journey for themselves and that they can own their voice and share their story, that that's part of what makes us great. If I played a role in that for some young people comin' down the line, then ... I'll feel good about it."