Proverbs 10:20 "The tongue of the just is as choice silver: the heart of the wicked is little worth."
Out of the abundance of the heart the mouth speaks (Mat. 12:34). The heart (attitude, mind) of the wicked is of small worth indicating the worthlessness of his speech. In contrast, the speech of the just, those living right, is of great worth. Their speech comes from a heart that has been cleansed by the blood of Christ.
The condition of my heart affects the quality of my speech. What is my heart like? Do I have a heart attitude that is pleasing to the Lord? My speech is the fruit of what is in my heart. I can testify to the truth of that. If I am angry, my speech shows it. If I have a loving attitude, people sense it and are much more receptive to what I have to say.
Our hearts are all filled with something. Either we are filling it with what our flesh wants or what God wants. Where our treasure is, that is where our heart will be (Mat. 6:21).
May our hearts be filled with the love of Christ (Eph. 3:14-21). May the fear of the Lord be our treasure (Isaiah 33:6). When it is, our speech will be as choice silver that will edify and give grace to others (Eph. 4:29). May our hearts be 100% yielded to the Lord, so He can sky rocket the value of our speech for His glory.