I hold my breath and try to force it out. I know it’s not entirely healthy, but it is a lot better then self harm. After a few seconds I release the breath, and get a nice little endorphin rush, which calms me down from losing my temper or doing something stupid.
I also try to get outside as much as possible when I am in a dark, or moody place. I go for a walk in the woods near my house and talk to myself, usually about my problems. If I don’t want to deal with them, I just tell stories to myself, or talk through one of the novels I am currently writing.
If none of that works, it’s onto the phone to find a friend, and then have them distract me, or listen to me vent.