What does it mean to decide "on purpose" to think a thought? How does that change the circumstance?

How do you decide “on purpose” to keep a thought? What does that mean? That I am deciding “on purpose” to be hurt by abusive behavior? All people, including the abuser, would agree that the situation is abusive/negative. Why does it fall on me to brush off someone who is trying to hurt me? Am I an “emotional child” if I decide to think a negative thought?