Ephesians 4:29 Do not let any unwholesome talk come out of your mouths, but only what is helpful for building others up according to their needs, that it may benefit those who listen.
"Most of Paul's moral exhortations are the sort that most ancient moralists uttered. Despite many points in common with the ethics of his culture, however, Paul often cites the Old Testament as his ethical authority. Ancient wisdom literature often emphasized learning to speak rightly; many sayings in proverbs emphasize the idea, including the encouragement to speak gracious uplifting words." - The IVP Bible Background Commentary
Proverbs 12:25 An anxious heart weighs a man down, but a kind word cheers him up.
Proverbs 15:23 A man finds joy in giving an apt reply— and how good is a timely word!
Proverbs 25:11 A word aptly spoken is like apples of gold in settings of silver.
It seems that many Christians still need this lesson from Paul. They think that they are doing the church a service by saying things to "improve" the church. How about just learning to appreciate what is already there? And if you have to speak, speak lovingly.