I sometimes feel as if I am surrounded by an aura of negativity at times. My life in general is overwhelming and to others, something they can't imagine living themselves. So, I feel that I am a good person to answer your question!
When I feel the black cloud hovering over me I try to sit up straight, take a breath so deep that my lungs and ribs hurt and exhale slowly. While doing this, I try to reflect upon what brought me to the moment that I am experiencing. Was it in my control or out of it? Did I contribute to the drama or am I a victim of it. Only I can answer these questions truthfully. No feeling sorry for oneself at this moment.
If I willingly came into the situation (which is often the case for me), then I need to figure out how to get out. What are my other options? Can I gracefully bow out and move away from the situation without making others mad? If I make others mad, is that such a bad thing? If I was drawn into the situation without wanting to be, I simply make up an excuse to exit and leave graciously.
For example: Let's say you and your partner have made plans with another couple. You meet for dinner and find that your partner and the other man are arguing about something that is becoming unpleasant for you and your friend and is drawing attention from the onlookers. You try nudging your partner's leg under the table or try changing the subject but it serves no good.
Excuse yourself from the table and breathe deeply while in the bathroom. Clear your head. Then, walk back to the table and say you got an urgent phone call from someone and have to leave right away (a friend is stranded somewhere or someone in your family needs a listening ear) and don't give too much information. Smile, apologize, hug goodbye and stay positive while exiting. When in the car, tell your partner that the tone needs to change or you will be going somewhere by yourself later (a movie or a coffee shop ,etc.) if they can't change the mood. Stick with your promise.
I've come to enjoy watching movies alone or listening to bands at coffee shops or restaurants and find my mood lifts right away. Hope this helps.