Tact is the knack of making a point without making an enemy. (Isaac Newton, 17th-18th century English scientist)
Some people are so certain of their knowledge and what they’ve learned from experience that they overwhelm others in any kind of discussion. They simply must make their point and they must do so with certainty and force. Not only is that tactless, which is bad enough, but it usually closes the door to further discussion that could be enlightening and helpful. Be assured but also be courteous.
Kind words are like honey—sweet to the soul and healthy for the body. (Proverbs 16:24)
Be tenderhearted and keep a humble attitude. (1 Peter 3:8)