In her upcoming memoir, Open Book, the 39-year-old singer opens up about why the events that took place on Halloween in 2017 led her to quit drinking for good.
The holiday began when Simpson and her husband, Eric Johnson, were on their way to a school assembly for their daughter, Maxwell, who's now seven.
"It was 7:30 in the morning and I’d already had a drink," she writes, in an excerpt obtained by People.
Following the school event, Simpson and Johnson returned home to prep for their Halloween party, but Simpson felt unable to help Maxwell and Ace, now six, get dressed ahead of the bash. The pair now share a third child, 10-month-old Birdie.
"I was terrified of letting them see me in that shape," she writes. "I am ashamed to say that I don’t know who got them into their costumes that night."
She eventually took an Ambien before bed and slept until they left the house the next morning. "I slept in, afraid to see them, afraid I had failed them," she writes. "I hid until they left, then drank."
In her book, Simpson reveals that later that day her friends came over and she told them, "I need to stop. Something’s got to stop. And if it’s alcohol that’s doing this and making things worse, then I quit."
"Giving up the alcohol was easy," she tells People. "I was mad at that bottle. At how it allowed me to stay complacent and numb."
What resulted was Simpson facing her anxiety and emotional trauma -- much of which came from the sexual abuse she endured as a child -- with a team of doctors, support from her parents and therapy twice a week.
"I found direction and that was to walk straight ahead with no fear," she says. "Honesty, it is hard but it’s the most rewarding thing we have. And getting to the other side of fear is beautiful."
"I had room for so many wonderful moments that I would have missed: sober for the first time ever in my studio and seeing Maxwell grab a guitar. Ace in pajamas he put on himself, proudly adding a sticker to his bedtime chart," Simpson adds. "There’s just no better gift. There’s no better gift I can give my kids, there’s no better gift I can give my husband. More importantly, there’s no better gift I can give myself."