It gets better.
Step 1. Close your eyes.
Step 2. Focus on breathing. In. Out. Measured. Even.
Step 3. Give yourself a hug. Keep doing it.
Step 4. Say to yourself (softly but aloud) “It will get better. It will get better.” Repeat until you suddenly realize your breathing is calm and peaceful without you having to think about it.
Oh crap — Step 0. Make sure you are in a quiet place with no interruptions. Public transit, not good; WC, better; home alone, best.