If it gets too chaotic and the kids are struggling to play, I try to structure the play with timers and number of kids that can be in a play center...I will also rotate the kids in and out of quiet play activities....Once the a child gets used to our routine things go fairly smooth, but if not, I only have to say "hey kids, does ms. xxxx need to help you all work out your differences"....that usually causes them to pull it together.
I also have a wooden chime I got from a Mary Jo Huff workshop and it works as well.
Calming myself down is much like teaching the kids to control their emotions....I have to remind myself to keep my hands to myself
and think about how I feel
and do not allow my emotions to cause me to physically harm someone