A unicorn's immune system is bolstered by their magic. Any ailments they develop simply dampen spellcasting until things work themselves out internally. Stronger mages tend to not get sick at all, but Trixie Lulamoon is not a strong mage.
Life is a performance for Trixie. Disasters must be kept backstage and away from audience eyes. But the curtains are closing on her solo act, and somepony needs to notice so they can hop onstage to help her. She's too proud to ask for volunteers.
Cover art is the fittingly named Worn Out by the artist Purmu
This is an entry in the Snippet Series, an anthology of old oneshots that I (and my good buddy Str8aura) wrote based around interesting pics I found. New ones will be posted every other Thursday for the foreseeable future.