A brother offended is harder to be won than a strong city,
and contentions are like the bars of a citadel.
With the fruit of a man’s mouth his stomach will be satisfied;
he will be satisfied with the product of his lips.
Death and life are in the power of the tongue,
and those who love it will eat its fruit.
Words of Death
Words of Life
Finally, remember that Satan only comes to steal, kill (sacrifice is the actual word) and destroy. And also remember that Jesus referred to him both as a thief and a liar (John 8:44, 10:10).
Finally, what does it mean in Proverbs 18:21, "and those who love it will eat its fruit?" In my opinion, the author is referring to both death and life. Which ever you choose to do: build up or tear down, you will eat the fruit of your labors:
Do not be deceived, God is not mocked; for whatever a man sows, this he will also reap. For the one who sows to his own flesh will from the flesh reap corruption, but the one who sows to the Spirit will from the Spirit reap eternal life. (Galatians 6:7-8)