This article first reveals that speech habits and happiness are closely related. Then it proposes three principles of speaking with happiness in accordance with Habitual Domain (HD) and communication theory. These three principles are interactivity, equality and integrity. Readers are encouraged to develop speech habits that lead to happiness in both the speaker and the listener. These habits consist of three NOs and three MUSTs. The three NOs are: 1. do not use negatives words; 2. do not use any words when losing your temper; 3. do not just speak of yourself. The three MUSTs are: 1. listen intelligently before speaking; 2. speak with sincere gratitude, using praise words; and 3. use rationality with kindness. The author suggests that home is the best classroom in which to practice speaking. It is recommended that the dialogue within family needs to be more friendly and gentle. Finally, the author uses four words of HD, " Awareness, Learning , Practice and Sharing" to encourage readers to develop good speaking habits.