"And the tongue is a fire, a world of unrighteousness."
James 3:6
Have you stumbled yet today? Maybe in choosing what to do with your time? Or in your thoughts? There are many ways to sin against the Lord, but as I understand it, James declares the man who controls his words to be "perfect." Not that he is completely without sin, but that the control he has on his tongue prevents further sins.
Consider this: to be angry is to speak and so act out of anger. If the anger is held in and not acted upon, then it can be dealt with easily with the Lord. No further damage has been done. Therefore, a person has controlled the whole body by way of his tongue.
Furthermore, those who are in authority must be careful because they speak with authority! To teach others is a great responsibility as many will be directed by our words. Teachers are judged with greater strictness (James 3:1), and rightfully so.
"And the tongue is a fire, a world of unrighteousness... and set on fire by hell (v. 6,7)." And, "No human being can tame the tongue. It is a restless evil, full of deadly poison (v. 8)." There is good reason, then, to remain quiet. Speak carefully when you have authority. Likewise, write carefully as our hearts are vocalized in this way also. By this, we are protected by God and bring Him glory by righteousness of speech. He has made it available through our silence. Memorize scripture and speak it instead. It will not lead you astray, but will in fact bind your heart and mind to God and redirect your deceptive heart.
"Even a fool, when he keeps silent, is considered wise; when he closes his lips, he is considered prudent."
Proverbs 17:28