Don't lose sight of the fact that new jobs/activities cause everyone anxiety to a certain extent but will probably lessen over time as you get to know the routines and have a bit more confidence in your ability to do the job. I use to get horrible stiff necks for the first couple weeks of a new job (try that, doing a new job in really bad pain :-) but I look down the road to six weeks or months and just concentrate on doing the best I can until then.