Umph, mfff, nnn, huffwupff, umvpppt . . . OK, all silliness aside, how many times did you hear the phrase "hold your tongue!" when you were growing up? Well, they didn't really mean to hold it, right? Cos if you did, you would probably sound like those first words that I typed up there. :) I bet it was usually when you were pretty young, and someone older either wanted you to hush momentarily, or they didn't want you to go down the path you were going, in the conversation.
Carpenters have a rule that they go by --- you may have heard it. "Measure twice, and cut once." In other words, make certain of the measure; check it a second time, and only then make your cut. It might be transposed in the light of these verses, to say "Think twice, speak once." I know that if I followed that mantra myself, I'd be a lot better off!
If we fill our mouths with praise and thanksgiving, and speak often to others about our Lord, then our speech will be gracious, and edifying as in Ephesians 4:29, and again in Colossians 4:6. Then, instead of our tongue being a fire, like in James 3:6, it will bring glory and honor to God. Matthew Henry's commentary notes that the person who "keeps a strong bridle on his tongue and a strict hand on that bridle, he keeps his soul from a great deal both of guilt and grief" and also can avoid bitterness and a poor reputation. The destruction mentioned in verse three can mean the loss of reputation, respect, or relationships. Those are all things that we should try to guard ourselves from losing, in order to be good servants of Christ.
Hmmmm . . . "Think twice, and speak once." I think I might need to write that on a card and post it here on my desk. And another one at the sink. And another one at the mirror. If ya'll will excuse me......