How we speak will often determine the level of blessing we enjoy in our lives. Now I do not speak of the way some mention words as if by our speaking we can create blessing and curse. This is the name it claim it crowd - who think merely mentioning we might be sick will insure we are because of our unbelief and our disobedience. This doctrine is just theological wind.
What the proverb is teaching us is that when it comes to how we speak - what we give is often what we get. On the good side of things, the man who speaks what is good and uses his mouth to build up and love others - will in turn enjoy that same good as it comes back to him. It is interesting that the proverb states the from the fruit of a man's mouth he enjoys good things. What is the fruit of the man's mouth - that is mentioned here? It is not just the words he speaks - but what they lead to that is the focus of this passage. We speak something or say it. Where does that lead? If we speak godless, critical, unholy words, we will most definitely receive a harvest from these words. That is what the writer of Proverbs is trying to tell us. Be careful what you speak - because there is a harvest of your words that is coming. You can enjoy good from what you speak - and you can experience bad as well.
There is a contrary aspect to how we speak. We read here of the desire of the treacherous man next. There are those whose mouths are filled with treachery and violence. They speak things that should not be said. Their mouths are used to injure rather than build up and encourage. Their mouths are unkind and unloving - and the end of their words is violence. How we need to see this and realize that our words and our mouths will pave a way for us. When we use them rightly our words pave the way for good things coming back to us. But when we become treacherous, deceitful, and ungodly in our speaking - it too will come back upon us - but only in the way of violence and problems.
Watch how you speak. It will determine what is coming to you in the end. Speak and act as those who know that they will be judged by God for every idle word we speak. That way you know that there is a harvest of your words that is coming - and you will receive your just dues based on the words that you chose to use - whether good or evil.