For example, a politician who campaigns on a platform of honesty and integrity but is later caught in a scandal would be an example of someone who doesn't practice what they preach. Similarly, a parent who tells their children to be polite but is often rude to others would also be a poor example of practicing what they preach.
The phrase can also be used in a more positive way, to encourage people to live up to their own ideals and standards. For example, a person who advocates for environmental protection could be said to practice what they preach by recycling, driving a fuel-efficient car, or taking other steps to reduce their impact on the environment.
Ultimately, the meaning of "practice what you preach" is about being authentic and consistent in one's actions and words. It is a principle that can be applied to all aspects of life, from personal relationships to politics and social change.