This was my submission for a 30 minute drawing challenge, where the subject word was 'remembrance'.
After careful consideration, my mind fell upon Princess Celestia and Princess Luna, and how, as immortal beings, they would be forced to witness the passing of countless friends over time.
I can only imagine that the most devastating blow for Luna would be the passing of her dear friend, Snowdrop, a blind pegasus whom Luna had befriended (before Luna had become Nightmare Moon), and who found the beauty in something as cold and bleak as snow.
Snowdrop gave everypony hope, especially Luna, who had been desperately trying to teach ponies to appreciate the night as she did.
But of course, when Luna became Nightmare Moon, she was imprisoned within the moon for one thousand years, and tragically, she never got to see her best friend again.
Snowdrop, as pure and kind as she was, was still a mortal, and passed away before Luna had a chance to say goodbye.
Remembrance is nothing short of a curse for Luna, missing her friend so dearly and unsure of what to do, but at the very least, she can find a bit of consolation in visiting Snowdrop's memorial and decorating it with a bouquet of flowers. Snowdrop flowers, that is.