Sit up straight so your tummy doesn't hang out. Thin is always in. You look so much prettier when you smile. Guys like girls with big boobs. Now that you've got your period, you's better be careful. I'd kill to have legs like yours. With negative messages bombarding our girls on a daily basis -- from misguided adults, from peers, from the media -- how can our daughters possibly feel good about their bodies? While you may not single-handedly be able...