If you've ever heard the phrase "the pen is mightier than the sword", you have been given good advice. In this world, nothing is more powerful than words. Even the Lord Himself chooses to operate mostly with a book.
This is why control of the tongue is so very important. With it, we have the ability to either create, or destroy. What we say is extremely important, taking second place only to how we say it. A lie can be spoken softly, and the truth can be delivered in such a way that it almost isn't worth saying.
Therefore, control the tongue. Mankind has mastered many a beast, yet still the tongue remains wild, free to wreak havoc across the globe. The sword can slay the body, the tongue can drag a soul down to the pit. Think about what comes from your mouth. What will the end result be? Will you deliver wisdom, or empower a fool? Will you boost confidence, or be the straw that breaks the camel's back? Will you save life, or will you take it? Every word you say has meaning, and thus it has power. You are carrying a loaded gun in your mouth. Ensure you practice trigger discipline.