"I was constantly bullied because of my looks, so I struggled a lot with my body image," Rumer reveals about being famous since birth. "I wanted to have no butt; I wanted to have no boobs. For a long time I just wanted to look tiny and androgynous. I never really shared what I was going through with my parents, because it was too painful. I didn't know how to ask for help or how to even bring it up."
But her mother, 52-year-old actress Demi Moore, eventually gave her a piece of advice that's stuck with her to this day.
"I do remember my mom telling me, 'There's always going to be someone who's a better singer. There's always going to be someone more fit. There's always someone who's going to be, in your mind, better than you -- who you're comparing yourself to. But you can't do that, because you will live such an unhappy life.' It just took me a long time to put that advice into practice."
Now, Rumer is coming out strongly against bullying.
"The real pressure comes from the Internet and social media -- the mentality that it's OK to attack people from behind a computer screen," she laments. "Strangers say the nastiest things. Until recently the thought of making one misstep that could be criticized would stop me from trying new things and from standing up for myself."
Obviously, Rumer was able to get over that fear to compete -- and win -- this season's DWTS.
"Dancing With the Stars helped me get over my fear of failure too," she explains. "The first day I danced on-air, I was nervous; I had been struggling, and the dress rehearsal hadn’t gone well. But after I finished I felt more beautiful than I had in my entire life. Not because of how I looked ... but because of what I'd accomplished and worked so hard for. When you conquer something you didn't think you could do, energy and confidence radiate out of you, and that's more beautiful than if you were skinny or had the perfect face."
These days, her haters rarely get her down.
"It's difficult, but the moment you stop saying, 'I'm really fat,' or 'I'm ugly,' and just say, 'Wow, I have this,' then you'll see a change," she writes. "We all need to stop bullying ourselves and being cruel to other women. Attacking one another instead of supporting one another has become the norm. Life's hard enough as it is."