Choose Your Tone of Voice
Be aware of the effects of your tone of voice. In counseling couples, I frequently point out how their tone of voice keeps changing. As a solution, I have them find a range of tones that their spouse finds comfortable.
The listener is always more sensitive and aware of the tone of voice than the speaker is. The more aware you are of your own tone of voice and the effect it has on the listener, the easier it will be for you to recognize when there is a change in your tone.
One way to become more aware of your tone of voice is to ask your spouse for feedback, by saying, "If my tone of voice ever distresses you, please point it out to me. And when you especially like a certain tone of voice, please tell me."