Don't hate nerves. Nerves are our friends. They give us the feed back - ouch, my lip hurts; I will stop playing the trumpet. If your cognitive function is intact, you will stop. Damage controlled.
Now the nerves you describe, are related to anxiety. This is a vital reaction that is important or continued evolution of the species. I see mastodon, I am scared, I will run, but first blow a note on warning long bone trumpet to warn tribe. Tribe is saved, you run into the forest, find a tree, hide and are saved. The tribal chief's daughter is given to you as a mate, you do and well... you evolve (to the next chiefteen daughter)... no I mean with the species, ya that's it the species.
Now I am not God, but this is how you get rid of it:
Breath repetitively into a paper bag until you feel all tingly. Then stop. The CO2 rush is a blast, you dig it and you play on dude.
1. Start with a muscle group furthest away from your body - the toes.
2. Flex them on one foot (right) very tight for 10-20 seconds.
3. Relax toes, and feel the warm blood flow back into them while breathing slowly
4. Hyperextend these toes
5. Repeat step 3.
6. Move to the other side repeat steps 2-5.
7. Move to next muscle group on right (the ankle); repeat sequence 1-6.
Once lower extremity groups are completed up to the hip, repeat sequence 1-7 starting with fingers.
Once this is completed to the shoulder, go to the forehead and start tensing these muscles, next the eyes, next the nose, next the jaw, then the neck (looking up, then down, then to right shoulder then to left shoulder) and you are done. Do these AT LEAST every 2 days, and you will be forever calm. This will also lower your blood pressure - no kidding!
But if you don't have the time because you are always playing the trumpet or running from your own mastodons (the significant other perhaps) then USE THE BAG!