Her horn stops glowing, Celestia's head lowering as she sighs. She is tired. Tired of this... tired of losing students. Twilight's pained face, eyes red as her horn flashed with her magic -- the last moments Celestia saw Twilight still playing in her mind often. She was simply... doing as Starswirl taught her. That interdimensional travel, time travel... any, of these kinds of magics, were dangerous. That even trying to say goodbye was a risk.