As explained earlier, young untrained wizards can trigger uncontrolled magic when they are in the state of heightened emotions. But emotions also affect trained witches and wizards and their magical abilities. For instance, in "Half-Blood Prince", a heartbroken Nymphadora Tonks temporarily loses her power as a Metamorphmagus when Remus Lupin starts distancing himself from her. The form of her Patronus changes to reflect her depression. Another example is Merope Gaunt, who only demonstrated any magical ability when removed from her father's oppression, but then lost it again when her husband abandoned her.