I am a stresser. At one point the stress caused mental conditions-panic attacks, pinched nerves, bowel dysfunction, even infections. So I had to relearn a few things.
First and foremost, Worry is a needless action. If you aren't going to DO something about the source, then it doesn't warrant worrying. It serves no purpose, it's internal and it's damaging.
Second: Take honest control of the situation. Use assertiveness. No one can read your mind when you are stressing, so verbalize it, control it.
Third: Meditate. It doesn't have to be something out of an eastern culture handbook. Just sit or lie quietly, listen to your own breathing, visualize it and make a point to relax.
I am still a stresser-I'm high strung by nature. But by taking control of those things that trigger negative reactions, I eliminate those reactions or, at least, diminish them considerably.
Final thought: If you are not directly affected by things going on, just say Fuck It and know that there will always be wrongs, always be assholes and always be another day. Then eat a candy bar