turn over a new leaf

turn over a new leaf (third-person singular simple present turns over a new leaf, present participle turning over a new leaf, simple past and past participle turned over a new leaf)

1. (idiomatic) To engage in self-improvement; to begin a good habit or shed a bad habit.

   Every year he resolves to turn over a new leaf and start exercising.

• start with a clean sheet

• (determination to do what is wrong or destructive): break bad