As my teacher once said, “If you can’t control your mouth, there’s no way you can hope to control your mind.’ This is why right speech is so important in day-to-day practice.
In positive terms, right speech means speaking in ways that are trustworthy, harmonious, comforting, and worth taking to heart. When you make a practice of these positive forms of right speech, your words become a gift to others. In response, other people will start listening more to what you say, and will be more likely to respond in kind. This gives you a sense of the power of your actions: the way you act in the present moment does shape the world of your experience. You don’t need to be a victim of past events.

Thanissaro Bhikkhu
from the book Noble Strategy.