Psychology of Manipulator

Just understand the psychology behind some manipulators. first one is they want to satisfy their ego if they love somebody they want to get the love for sometime only and not for the lifetime. they  have some ego like why she left me even I am good and better than the other person. generally they want to attack the psychology and they want to break that trust between the couple and they want to play in their life and in the name of well wisher. We cannot identify them easily. Whenever we suspect them, they act like wise people.