James 3:2 For in many things we offend all. If any man offend not in word, the same is a perfect man, and able also to bridle the whole body... Even so the tongue is a little member, and boasteth great things. Behold, how great a matter a little fire kindleth!  And the tongue is a fire, a world of iniquity: so is the tongue among our members, that it defileth the whole body, and setteth on fire the course of nature; and it is set on fire of hell.  For every kind of beasts, and of birds, and of serpents, and of things in the sea, is tamed, and hath been tamed of mankind: But the tongue can no man tame; it is an unruly evil, full of deadly poison.  Therewith bless we God, even the Father; and therewith curse we men, which are made after the similitude of God.

What we say turns our whole being.  It is vital that we yield this member, this tongue, to the Holy Spirit.