        The Princess looked at Twilight slightly sadly.  “I would love to have you by my side, truly I would.  However, Princess Luna was quite insistent that it not be so, and her reasoning is sound.  She believes that if the spell were to go awry, you are the only unicorn in Equestria who might be able to mount a rescue.  She also believes that if I should somehow lose my connection with the sun—even briefly—that she and you can, in tandem, correct its course, if needed.  Of course, neither of us expects that to happen, but it is best to be prepared.”