I've known this for many, many, many years but it always astounds me when I pay attention to it. The "it" I am referring to is the tone of voice you use when you are talking.
You can say the same words and convey SO many different meanings just by the inflexions and accents you put on certain words. You can make your tone, kind, indifferent, sarcastic, uncaring, distracted, loving, hateful, mean, jealous...etc. All without changing a single word in your sentence.
I particularly notice this when I am talking to my kids. Some of them are getting to the age where I can mix more and more of a friendship in our relationship amongst the parenting. I'm sure you all know what I mean, if you get an imbalance between the friendship and the parenting at too young of an age the children will sense the lack of leadership and start to try and lead. They crave structure.
My point is, I try and speak kindly to my kids, but if I am in a hurry, or it's the MILLIONTH time I have asked them to do the same thing, the words stay the same, but the tone changes....big time.
But if I point out to my kids that I am trying to be kind, they seem to be more likely to accommodate my desires without the big ordeal.
It's not always easy to remember that the TONE I use is just as, if not more important, than the words I use.
I am still a parent in progress, but I hope I am better tomorrow because of what I learned today.