Article continues below advertisementDemi Moore is opening up about how tough it's been to watch ex-husband Bruce Willis amid his dementia battle.Article continues below advertisementOn Tuesday, September 2, The Substance actress joined Oprah Winfrey on "The Oprah Podcast" in a pre-recorded segment. The sit-down was part of a larger interview with Willis' wife, Emma Heming Willis, about her new book The Unexpected Journey: Finding Strength, Hope, and Yourself on the Caregiving Path."It's difficult.