break a habit 戒除习惯；戒除（坏）习惯

【例句】
When you break a habit that you have been doing for a long time your mood will improve and your life will become better almost instantly.
改掉了一个长期的坏习惯，你的心态和生活都会立马得到改善。

Once you decide to break a bad habit, stick with your decision.
一旦你决心要改变坏习惯，就要坚持你的决定。