Jessica Simpson Decided to Quit Drinking After Realizing She Couldn't Dress Her Kids for Halloween

At 37, “I thought I was too young to write a memoir,” Jessica Simpson says. But within weeks of getting sober in late 2017, she began writing her story, the upcoming Open Book.

“I didn’t realize all the stuff I had to say until I was actually connected to it through music and writing,” Simpson tells PEOPLE. “So when I started to go through all the depth of the pain that I was experiencing, I realized I was pretty rock bottom.”

That was Halloween 2017. As she recounts in her book, she and her husband Eric Johnson were on their way to a school assembly for their daughter, Maxwell. Simpson was in the passenger seat.

“It was 7:30 in the morning and I’d already had a drink,” she writes.

From there, she and Johnson went home and prepared for the Halloween party they were hosting that evening. Simpson dressed as her pal, country star Willie Nelson. As her team glued a gray beard on her face and put on her wig, grey with long braids, she “zoned out.”

When Johnson asked her if she wanted to get the kids ready, she realized she was not in any state to help out.

“I was terrified of letting them see me in that shape,” Simpson writes. “I am ashamed to say that I don’t know who got them into their costumes that night.”

That night, she took an Ambien to help her sleep. The next morning, she writes, “I slept in, afraid to see them, afraid I had failed them. I hid until they left, then drank.”

Simpson’s close circle of 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.”

Her friends gathered around her and mobilized to help. With a team of doctors, the support of her parents, and twice-weekly therapy, Simpson began to face her anxiety and the emotional pain that had haunted her for years. Much of the pain stemmed from the trauma of sexual abuse she had survived as a young girl. Pain that had often led her to reach for a drink.

“This feeling of being alone and scared in the dark was one I’d had since I was abused as a child,” Simpson, now 39, writes.

As she recounts in her memoir, she has quietly reclaimed her life and her health over the past year.

“It was a long, hard emotional journey,” she says. One which resulted in the book, as well as six new songs that will be released along with the audio book she narrated.

And Simpson, who runs her billion dollar clothing line, has found new joy in being present for her husband and their three kids: daughter Maxwell, son Ace and baby Birdie, 10 months.

“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.”

“There’s just no better gift,” she says. “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.”

For more from Jessica Simpson and an exclusive excerpt from Open Book, pick up the latest issue of PEOPLE, on newsstands Friday.

If you or someone you know is struggling with addiction, please contact the SAMHSA substance abuse helpline at 1-800-662-HELP.