Think in full sentences before you speak in half ones.

Half formed speech makes people work out what you meant, and they often get it wrong. The thought arrives faster than the words, so you start talking while still assembling, and the result sounds less certain than what you actually think. Finishing the sentence in your head first is a small delay that changes how everything you say is received.

Try pausing for two seconds before answering anything that matters, long enough to know how the sentence ends. In writing, read it once before sending. You will say less this week, and more of it will land the way you intended.