Angels are not the pure, virtuous creature that they are popularly believed
to be. To become an angel, one has to have lived a 'pure' life up until their
mortal death and must be white on their gray status. Because humans are
not pure natured, angels are usually people who died young and did not
live long enough to gray into black.
But once someone has become an angel they find that their 'evil'
tendencies increase dramatically, along with all of their senses and
emotions. They are extremely emotionally driven and often come off as
juvenile. This is the same for both demons and angels. Because of this
angels usually don't stay white very long.