A sister in our ward told an incredible story about her daughter in the Relief Society lesson.
She has eight kids; one of her youngest started into her terrible twos and never left them. This daughter, we'll call her Katie, became a preschooler and continued to be a holy terror to her parents. She fought with her siblings, talked back to her parents, disobeyed all the household rules, couldn't be taken out in public, threw things, hit others, and was just all around a very difficult child. The mom didn't know what to do with her so she prayed. In her prayers she felt that she needed to positively reinforce the good but she also felt impressed to help Katie realize her potential.
Every night, just as Katie had fallen asleep, the mom would go into her room, kneel by her bed, and quietly tell Katie what a kind, gentle, obedient, helpful, beautiful daughter she is. She would use adjectives that certainly didn't describe Katie right now but they were adjectives full of hope for how Katie could be.
Within a few days this mom began to notice a difference. Katie was becoming kinder to her siblings, she was more gentle and more patient. Her tantrums lessened and her obedience increased. The mom continued to enter Katie's room every night for almost a year and quietly tell her of her potential. Katie's behavior continued to improve during that year. Now Katie is all grown with children of her own. She and her mom are best friends and Katie is the kindest, most gentle and patient of all her siblings. It's amazing all the good that came out of those little nighttime whispers that reminded Katie's spirit of her incredible eternal potential.