Isn't is amazing how the same truth is found in many places. I find this Sioux principle is a principle in the Bible as well. Ephesians 4:15 tells us to speak the truth in love.
"O Lord, who may abide in Your tent? Who may dwell on Your holy hill? He who walks with integrity, and works righteousness, and speaks truth in his heart. He does not slander with his tongue, Nor does evil to his neighbor, Nor takes up a reproach against his friend." Psalm 15:1-3
May I always check my heart before I speak. Even if I must speak correction or disagreement or establish a personal boundary, can I honestly say it is in love? If I can then God is pleased. Now to work on word choice . . . but that's for another day. ;-)