Isn’t alignment just another part of your personality? Yes
and no.
Certain personality traits have moral weight, particularly
those that influence how you interact with others.
Cruelty and generosity can be considered personality
traits, but they’re also manifestations of your beliefs about
the importance and worth of other people. A character
who aspires to good might have a cruel streak, but if that
streak manifests too frequently or in extreme ways, it’s
hard to say he’s really upholding his moral ideals.
Other personality traits have no moral weight at all. A
fastidious and well-organized person can just as easily be
evil as good. An impulsive prankster can also be good or
evil. These quirks of personality are mostly unrelated to
alignment, but your alignment might affect the way your
personality translates into action. An evil prankster might
favor cruel practical jokes that cause personal harm and
damage property, while a good one would steer away from
such injurious acts.