Letters From a Vampyre part two

We rejoice, it works,
  the cure works.
Finally, we can live normally,
  except the one day each month,
when the cure wears off,
  that we have to feed.
Only the ones who
  care not what they do
have not taken the cure.
  Now we can live pure,
except our one curse.
  The curse is this,
on blood we were born,
  and on this we must survive,
without it we cannot live.
  With this comes
the blessing or curse,
  of exceeding long life.
To some it causes much strife.
  We fight with our own kind,
just to help those who want the cure.
  Without our help,
the Others would rule,
  and humans would play the fool.