Personality Change?

So, the story is almost done, and one of the characters suddenly wants a personality change. He's supposed to be gruff and hard to get along with.  His personality has already been shaped and at the last minute, he decided he didn't want to be so gruff anymore! Ugh! That means I'll have to go back through every chapter and rework his personality! What do you do when one of your characters suddenly decide they want a different personality? Do you stick with what you originally had in mind? Or do you test the new personality to see if it's better than the old one?