I would try and figure out what is causing me to get all riled up in the first place. If it's something that I could fix, I would do that.
If I had no control over the situation, I would decide if there was something else I could have done - did I do the best I could do? If so, I would let it go. If there is something I could do now, I would see if it was in my best interest to fix it or just let it go. Then you just take a breath and just breathe.