Here is one of best quote describing about what we ought to say.
Learning to think first about the meaning of it before we spit it out which should be encouraging, benefited rather than destructive to other.
First learn the meaning of what you say, and then speak.
Epictetus was a Greek Stoic philosopher. He was born a slave at Hierapolis, Phrygia and lived in Rome until his banishment, when he went to Nicopolis in northwestern Greece for the rest of his life. His teachings were written down and published by his pupil Arrian in his Discourses and Enchiridion.