One of my hobbies is woodworking. I love the smell of fresh wood and the tangible nature of seeing something created from start to finish. The golden rule of woodworking is measure twice, cut once (and also, as I’ve been told at conferences where I speak, don’t cut off your fingers — ha!).
You can always cut off more material if you need to, but you can never add more material if you make a mistake.
Communication is very similar. Once spoken, words cannot be taken back. “I didn’t really mean what I said,” is a terrible way to try and escape from a painful/hurtful statement. Regardless of intent, the truth came out and there’s no taking it back.
Listen twice, speak once. Listening is measuring, speaking is cutting. Be sure that you know what you’re speaking about before you open your mouth. And in most cases, listening and reflective feedback (this is what I heard you say — not what I interpreted you saying) is way better that speaking your mind.