Idealization and devaluation are two different ways that people think about other people and things.
Idealization is when you think of something as perfect or almost perfect. It means you thinkreally highly of that thing or person. For example, if someone loves their grandma, they might idealize her and think she is the best grandma in the world.
Devaluation is when you think something or someone is less valuable than they actually are. It's like downgrading someone or something, like thinking your grandma isn't as nice as you once thought.