There are two types of stressful situations: situations you cant control, and ones you can at least do something about to improve the situation. First figure out what is causing you to feel agitated and if it is something you can or cannot influence.
Is the stressful situation caused by circumstances you cant control? If it is, remind yourself you can cope with whatever happens, if indeed it happens. Now is the time to take care of yourself as best you can. If possible, remove yourself from the stressful environment. It may be that relatives are arguing, for example, and you can step away from this situation and find a more peaceful, nurturing environment. Take several slow, deep breaths, and perhaps even meditate or listen to a relaxation tape. Find distractions that are nurturing to you and healthy for you. You might for example, spend time with your pets, go for a long walk outdoors, take a soothing bath, or do something creative like paint, play music, or work in your garden. Gently bring your thoughts away from what you cannot control, to things you can control.
Is the stressful situation about things you can or need to do something about? Take a few, very...