Nickname

I had always heard that names have power, but it wasn't until I nicknamed my cat that I realized it was true.
Sweetie was the nicest cat I had ever seen. Then one day I came home to find that she had knocked my mom's potted plant off the table. I picked Sweetie up and scolded her, calling her Sweetie the terrible.
In the blink of an eye, Sweetie became a monster.
Hissing and clawing, she got away from me and began terrorizing the house.
Furniture was destroyed, documents ruined, my formerly gentle cat had become a terror.
All because I jokingly gave her a nickname.
Since then, I've tried to be more careful with names. But there have been times when a nickname has slipped out.
Francine became terrified of everything when I called her a scaredy cat late one night while we watched a movie.
My cousin Peter hasn't grown any taller since I called him little guy at the family reunion three years ago.
This ability even seems to work on pre-existing nicknames. When I met Dash, I thought that was his real name. But after I called him that, he suddenly became impatient and jittery, unable to stay at one task for more then a few moments before growing frustrated.
To make things worse, no one seems to notice the changes my nicknaming brings except me.
Though I remember Sweetie as she once was, all my family recalls is the beast she became.
My urge to nickname keeps growing, and yesterday I learned something about this ability that makes it even harder to resist using.
It works when I nickname myself.