I could have laughed it was so simple. It wasn't bitterness the pet had just displayed, but genuine bewildered fright. I'd changed. I was no longer the known Jang girl with long scarlet hair, willowy waist and exotic bosom, all beauty and physical grace. I was this lank, thin, paste-faced twig of life. It didn't know me. Farathoom! I probably even had a different smell!
-- Drinking Sapphire Wine by Tanith Lee
That's because the change was so sudden. If the overall change had been extended over a period of years, little bit here, little bit there, it would've gone unnoticed. But a frog will notice if he's thrown into a pot of boiling water.
It makes me think of a philosophy professor I had. He would talk about crimes and how the person who commits a crime at, say, age 12 is not the same person at, say, age 30. That person hasn't just changed and evolved mentally and emotionally. Physically, cells die and cells regrow. That person is an entirely new person who is not guilty of the crime committed many years earlier.