When something in our bodies (atomic nervous system) reacts to our fear of whats around us, or what we think of; it makes our body go into this state of readiness. This state of readiness is the biological way our bodies get ready for a threat around us and prepares us for a brawl or a chance to run like hell. We call this the "Fight or flight" response.
Seeing as we no longer need to use such a system because we aren’t living in caves and hunting for our own food, us modern day people, still have this response. Its not a very good thing if the body gets ready for a fight, that's not actually going to happen. in a way, its like you’re wasting its time, and it doesn’t like it.
After the flight or flight effect happens, there is another process in which is the opposite of what happens in our system that creates the flight or flight effect, to make the effect go away. That other system only happens when we have done something where the body works its hardest to survive and fight for its life.
Its the same other thing that makes it possible so you don’t feel pain when you are in a fight until the fight is over. I'm sure you can remember a few times lol. This system resets the body into a state of calm.
What happens in anxiety now, is that since we no longer run away from the threat we are making up in our mind(stress/anxiety) based on the thing that troubles us, the fight or flight system still happens, but there is no other system to reset the body like I said earlier, and it can cause the body pain.
ways to rid your anxiety and pain is quite simple really. Well, for the most basic parts really; Would be to EXERCISE!~ When you exercise, you mimic a good fight or a hard sprint from danger (work out), and that system I spoke of earlier that helps reset the body, has a chance to do its thing and set your body at ease. Its a good practice to work out at a gym or do a lap or so around the block, before doing something that makes you anxious or nervous. It will greatly reduce and help prevent full on Anxiety attacks. Hope this long answer helped.