"Watch for anger of the body: let your body be self-controlled. Hurt not with the body, but use your body well.
Watch for anger of words: let your words be self-controlled. Hurt not with words, but use your words well." -- The Dhammapada
The first part, not using unnecessary violence, is well known to most practitioners of martial arts. The second, I feel, is a beneficial outcome of a martially disciplined mind.
Words can damage as much as a fist; they cannot be taken back--just like a punch thrown at a target. Most people think this means aggressive, rudely phrased words--yelling and screaming. But in truth, subtle quips, negative comments, and frequent jests can erode another's self worth over time.
A teacher must be aware of this; a student, a friend, a parent, or a spouse.
In a dojo setting, for example, this does not mean giving endless praise to one's students. Nor should a training partner have only non-critical words for his/her partner. However, I have known many individuals who have stopped doing something they loved because of words either said or not said.
"Speak the truth, yield not to anger, give what you can to him who asks..."