6 Months after Twilight's rescue
The bright sunlight of a clear summer day poured through the windows of Twilight's library, illuminating piles of scrolls and opened texts. The lavender mare herself sat in one of the numerous chairs pulled up to the table, her eyes transfixed on the reports in front of her. To a less-educated pony they would be gibberish; to her they told a comprehensive accounting of Equestria's status as a nation. She absent-mindedly pulled a hoof through her rose-streaked mane, disturbing a single blue feather unobtrusively braided amongst the strands, causing it to graze the side of her face. Feeling its presence, she sat back from her work to gaze into the cerulean expanse of the cloudless atmosphere. A smile slowly spread across her face as her thoughts turned to a certain weather pony.
She craned her neck behind her to call to her dragon assistant. "Spike! I need you to take a a letter for me." The young dragon hurried to her side, quill poised above parchment.
Dear Princess Celestia,
I don't think I need to tell you that this has been the most difficult time of my life. After I lost my ability to use magic, I thought I had lost my reason to live. My wonderful friends did their best to make me feel useful, but it never really worked. I thought I had lost everything; I was certain that without my magic my friends and even you, Princess, would abandon me. I was convinced that without magic I had no purpose.
Fortunately, I no longer feel this way. Time has its own power to heal, and there has been time for me to come to understand that the magic of friendship is more powerful than that which I lost. My friends were never in danger of leaving me, no matter what I thought in the midst of my confusion. I lost my magic, but I still have everything else.
Since you named me your personal advisor and placed me in charge of Canterlot's libraries and archives, I've found my purpose again. I feel like I belong, like I contribute. With that in place, and my friends and my special somepony at my side, I don't truly feel like I lost anything. I have everything that's important to me right here.
Thank you, Princess, for giving me this second chance.
Your Faithful Student,
P.S. - Rainbow says 'thank you' for the anniversary cupcakes.