I do not feel the word should exist. A mistake by definition has a negative connotation that implies an accidental error. A "mistake" should be considered a learning experience which, in all actuality, is a good thing. However, if you were to make the same "mistake" again it really wouldn't be a mistake because you should have known better. Instead the mistake was sheer negligence.
Other subscribers who dislike this word:
Gabriela S. (United Kingdom of Great Britain and Northern Ireland)