Dear Princess Celestia and Princess Luna,
This past week has been the worst ordeal of my life. My friends are all concerned about me, and none of them can understand why I'm so depressed. I tell them I feel guilty about what they've had to endure, but of course they don't comprehend the true meaning of my words. My friends don't even know the scope of their own sacrifice. Worst of all, I suspect they would willingly have made that sacrifice, just to help me, if only they knew how important it was.
It's ironic that I've finally managed to achieve what I set out to do years ago, and purely by serendipity (a.k.a. Bubble/Pinkie somehow picking the one set of coordinates that mattered). Yet at the same time, what happened to my friends is still my fault. I never should have disobeyed you, Princess Celestia. Somehow, my friends seem to have come through this thing unscathed, so I guess you were right. Things are pretty much back the way they used to be in this universe, except of course for me, and for the secret that the three of us now share.
Princess, when we were standing in the library, and you told me to remember why I first studied magic, it felt like a slap to the muzzle. At the time, I thought your choice of words was a careless mistake. Now I realize you wanted it to sting. You wanted it to leave a mark on my heart, and it did, and for that I'm grateful. The sooner I can let the pain in, the sooner I'll be able to achieve some kind of closure. I'm still hoping that's possible.
Ever since I can remember, I've been pushing myself to learn everything about magic for one single, focused reason. Princess Celestia, until Princess Luna learned about it earlier this week, you were the only pony I ever entrusted that secret to. (Your counterparts, I mean.) I never told my family, not even my BSBFF! I suppose I felt like it was so shameful that I had to hide it forever. I'd hoped that the most talented mage in the world would be the pony who could help me reach my dream. I'm ashamed to say it, but your young Twilight Sparkle didn't bare her soul to you because she trusted you, Princess; she did it only because she was desperate. I suspect you knew that all along, though.
Why did it have to be one of those rare things magic just can't do? I knew magic didn't have the solution even before I moved to Ponyville, but I kept trying anyway. I spent years researching transformation magic, and I even became proficient in changing species! To this day, I still don't understand why it won't work. Magic is the most amazing of all the sciences, but it's also the most fickle and frustrating.
I don't know if I'll ever be able to tell my friends the truth. Of course I want to tell them, but what would they think of me? Even worse, would they start to remember? Would they begin to suffer the same way that I did, the way that little preschool-aged unicorn suffered, friendless and alone, pushing herself like mad to lift things with magic when most unicorns can barely read? I can't let that happen to anypony else, especially not my friends. Perhaps with time, and with your assistance in dreams, Princess Luna, I'll be able to tell them. But it won't be anytime soon, and until then I will wear this delicate tiara on top of my petite little head, and I will do my damnedest to bear its crushing weight.
Thank you both for forcing me to do what needed to be done: the memory alterations to fix the disjunction between my friends' bodies and their minds, the lies we had to tell them, and every filthy ethical transgression we had to commit in order to put things back the way they needed to be. Was rewriting my friends minds with their double's memories honestly any different than sending them back? Given that everything else in their minds is symmetrical, memories should be the only difference, right? It should be the same, logically speaking, but I can't say with confidence that swapping two otherwise identical pony's memories is the same thing as swapping their minds entirely.
I know you believe that this was for the best, Princess Celestia. It's certainly more convenient and less heartbreaking than having five transgender friends who would most likely be suffering as badly as I've suffered. But you have more than a thousand years experience in setting your emotions aside for the common good, while I remain haunted by the decision I have made. Please forgive me for everything that led to this, if either of you can. I know it probably sounds silly, but it would mean a lot to me.
Perhaps someday I'll be able to enjoy the fact that I'm finally a real mare, without all of this terrible guilt.
Your friend,
Prince Nightfall Twinkle
Princess Twilight Sparkle