When you decide to do something different to change your life for the better, you are turning over a new leaf. Example: "This year I've joined a gym and I am exercising every day. I'm turning over a new leaf."

Turning over a new leaf is like turning over a new page ("leaf") in your life and seeing what is on the other side. Example: "Wow. Look how polite your son has become." Reply: "Yes. We had a big talk with him, and he has really turned over a new leaf."

You turn over a new leaf when you commit to changing your life for the better. Example: "I'm turning over a new leaf: I've decided to quit smoking. "