Valium. Seriously. I avoid people that I know will stress me out, as an example my neighbor who is a very intense person. When she speaks she leans forward, talks loudly and animatedly, and in general seems to be worked up about something all the time. Frankly, people like that wind me up and then I get anxiety. It's too costly in terms of stress and subsequent exhaustion. I also avoid situations like going to Wal Mart on a Friday, Saturday or Sunday unless it is late at night. Rude, oblivious people drive me nuts. So for me avoiding people and situations that I know will get me on edge helps a lot.
But sometimes you can't avoid people or situations, and you have to learn to deal. I have developed a wonderful ability of 'listening' to people without actually registering a word they say. All I hear is 'wahnk wahnk wahnk' like the teacher on Charlie Brown

I don't know how to tell you to tune people out, it isn't something I can explain. But if you can learn to do it, it helps. The oblivious or rude people? Push their cart out of the middle of the aisle, or simply say 'pardon me' or 'perdon' and squeeze right on through.
I have little things I do that calm me and soothe me too. I knit, I listen to music that I really like, take a kitten or chick and play with it, maybe groom my house plants. Make it quiet in your home, don't let noisy, tense or fractious people in.
And ask your Dr. for some ativan/Valium. You won't get addicted if you are responsible with it, I've taken it for years and often I go months at a time without taking it, but if something happens like happened to my family last week, I take one. The last prescription I got is several months old and still is about 3/4 full, I should probably toss it out because it's getting old. Anywho, it improves the quality of my life and alleviates my misery until the crisis passes.