Self soothing is one of the most important skills to help improve your relationship. When your partner says something that you do not agree with or feels threatening in some way, you will probably notice that your mind may start to race with thoughts to combat his/her point of view or evidence to prove her/him wrong. Your muscles may tense up as if you are in a fight and you have to run or attack back. Your heart may start to pound as you anticipate a struggle of some sort. In this physical and psychological state it is highly unlikely that you are going to be thinking clearly or making comments that are helpful to the couple.
This is where you need to do the following to calm yourself down:
1) self talk: Remind yourself that this is just your partner's opinion and you are entitled to have your opinion. You do not have to do anything with which you do not feel comfortable even if your parter gets angry. Both of you have been angry at each other in the past and you are still together. The best time to talk is when you are calm and not in the heat of the moment.
2) breathe deeply: this will slow down your heart beat and help you to relax even though you are feeling stressed by the interaction. It is not helpful to exaggerate your deep breathing to your partner although you do not have to hide it and if asked about why you are doing it, a good response is "i want to be calm so i can best hear what you are telling me and be able to give it the consideration it deserves."
3) remove yourself from the situation if you know that you are not going to help the situation with what you have to say. Try to do this gracefully and not by slamming the door-You might say: "I think i need to take a walk and calm down so i do not say anyting that will not be helpful or i will regret later.
By self soothing, you will have a better chance of having a positive interaction than if you start to tell your partner to calm down as you will be serving as a model for how to deal with difficult feelings.