Breathe. Focus on your breathing. Slow and methodical. With practice you'll be able to activate the vagus nerve and the parasympathetic nervous system to slow your heart rate and "calm your nerves".
Some people count or have a mantra as they breathe. Others pray. Do what you have to so that all you focus on is each breath. Sweet dreams.
Me:44 W:38 T:10.5 M:7.5 D:3 BD: 7/2015 W moves out of MBR: 9/2015 WW files for D: 2/8/2016