if you dont have anything nice to say, dont say anything at all

If you dont have anything nice to say, dont say anything at all is more than likely a phrase you have heard at least once in your life, probably by your parents, grandparents or another close family member. What this phrase means is that you should only speak kindly and politely to others; if you feel the need to say something rude, mean, judgmental or insulting, you should just remain silent and not say the words if they are not nice.