How to have the best relationship

My friend said something profound to me the other day. I have been thinking about it ever since. She told me how she had spoken words of death in her home. She had cussed out her family and called them names etc. Now she realized that words can speak life to people. We can speak words of hope, encouragement, love etc. The words I speak are either words of life and breathe life into the other person, or the words are death and they destroy a relationship. For example, calling someone "stupid" speaks discouragement and destroys a relationship. Telling someone how much you love and care about them brings them joy and builds the relationship. I wonder how many divorced people could have saved their marriages if only they had spoken words of life, not death.