This was done for Ashes of Equestria, a setting in which Princess Celestia has vanished and the magic holding Equestria together is beginning to falter in the face of great evil.
 
Nurse Redheart feels it perhaps more keenly than most… her entire existence now is only to help others, not because she wishes to, but because her mind is incapable of processing any other way to press on.
 
The weight of duty crushes down upon her, and all she can do is try to reduce the suffering of others while doing nothing to alleviate her own sorrow. The medicine… it’s the only way she can bear it…