Don't say anything unproductive unless that is consistent with your overall motive. And if you find that your motives are negative, it's probably time to take a time-out and reassess the situation. The mark of a winning communicator is that they will skip the quick retort and give a productive response instead. Be consistently honest. People have a sixth sense about the character of others.
Winners always walk their talk.
Any inconsistency between what you say and what you do will be spotted and will become a measure of who you are. Others will have a difficult time talking and listening to you if there are questions about your honesty. The words of liars fall on deaf ears. If you make a mistake or there are misunderstandings, make corrections and clarifications promptly. Character is built.