A migraine attack generally brings on a sort of anxiety attack in the sufferer. They know how much it's going to hurt so their heart rate increases. This increase in blood flow makes the problem worse.
Once you've retreated to the quiet, dark area and covered your eyes from any possible stimuli then breathing is the next area to focus on. You must let your breathing relax. Panicked breathing will increase the pain you're already experiencing.
To allow your breathing to relax follow these steps:
1. Take a long slow deep breath and exhale equally slowly.
2. Again take a long, slow deep breath. As you're slowly inhaling focus on the sensation of the air filling your lungs. Feel the air filling your body. Once you've inhaled as much as is comfortable again exhale slowly. As you're exhaling focus on the sensation of the air leaving your lungs and escaping through your mouth. Breathe out completely.
3. Repeat the process of inhaling slowly, focusing on the sensation of the air filling your lungs and exhaling slowly 4 or 5 more times.
4. By the fourth reptition you should notice that your breathing is far more relaxed and calm. Your heart rate should now also have lowered back to a resting rate and you may even feel slighly sleepy. If so embrace that feeling and allow yourself to fall asleep.