Jesus Christ once while teaching told the people that it is not what comes in but out that defiles the body. This is of course true because the mouth happens to be one of the openings in the body that recounts our emotions. Things that we think about often time comes out through the mouth. When the mouth is not bridle, it could lead the owner into trouble. Remember being told by my grandmother about a folklore of the skeleton who said that it is his mouth that has kept him at this place.
More so, according to a manual of children's commentary words are not that evil just as fire us not always bad. This is so because the same that consumes is the one that a Goldsmith needs to make fine gold products. It's always about how it's handled. Hence, retraining the mouth from taking too much is a way to use the words wisely. Another way is ability to know how to use correct words in every situation. Solomon explains in Proverbs 10:19b that a righteous man or wise man studies how to answer. But it's however a different thing when compare to a wicked man who pours out evil. A wise man has self control in a way he uses his mouth. The person opens his mouth wisely and speaks wisdom. This means that he talks wisely at anytime. He operates by certain laws.
David for instance is seen praying that his speech and his thoughts would be pleasing and acceptable to God. He knew that he needed God's help in thinking and talking the way he should. Little wonder people say that before one say a thing, he should think whether the word would heal or break, whether it will be hurting or even kill.