Numbers that can't be divided by anything but themselves and one. Like 1, 3, 5, 7, 11, 13... I actually taught my best friend his prime numbers because he sat through my panic attacks with me.
Basically, you've got to focus on something repetitive and makes your mind work and focus on something else. If I get really mad, I start repeating back the Fibonacci sequence to myself because it's more complex and gets my mind off of things better. Math might not be up your alley, but it certainly helps me.