Emma Heming Willis never expected her life to look like this.

Thirteen years after she married actor Bruce Willis and about a decade after she gave birth to their two daughters, Mabel and Evelyn, Heming Willis publicly revealed a devastating secret. Bruce was taking a step back from acting because of aphasia, or damage to the parts of the brain involving language.

A year later, she had a crushing update: Bruce was suffering from frontotemporal dementia – primary progressive aphasia, to be specific – the name for a group of brain disorders that occur due to frontal and/or temporal lobe decline. About 50,000 to 60,000 people have FTD in the United States and it causes personality changes, can lead to speech problems and is incurable. People live for about 7 to 13 years after symptoms start.

Now, the 47-year-old former model is offering us a peek into her journey as a caregiver, with a prescriptive book of tips she wishes she would've known: "The Unexpected Journey," out now. One message is loud and clear: Caregivers – 1 in 4 adults in the United States – need more support.

"I didn't know anything about caregiving prior to becoming a caregiver," she tells USA TODAY. "I didn't really know much about FTD until I needed to know about FTD. And you're just thrust into this seat, and you have to figure out so many things so quickly in real time, and then you figure it out, and then you're stable, and then all of a sudden, the next shoe drops."