Having a new job is always very nerve wracking. This is a normal feeling that I know that everyone has. You want to do the best job that you can and you over scrutinize every thing that you do. I wouldn't look at this as a negative. I am certainly glad that people care about their work. I know from experience that this care is very fragile and can quickly turn into raging self doubt. First off, remember - People Make Mistakes. We are not machines. We cannot always do things as accurately as we need to. What makes us better than machines is that we can learn from our mistakes. Recovering from mistakes is simple if you have confidence in what you do. Like most people, my confidence level fluctuates. Some times I am very confident and nothing bothers me at all. I fix the mistake and move on. Sometimes, mistakes stick with me. When you have low confidence in your abilities, mistakes and even the threat of mistakes can really be challenging to overcome and let go of. Having confidence in your ability to do your job the right way is to me the best way to overcome the gloom and doom of mistakes and potential mistakes.
I work in a very high stress environment where lots of money and peoples lives are at stake (I am bridge engineer - translation NERD!). I need to have confidence that what I am doing is correct. I can not dwell on doing something incorrectly. I also do not have the time nor resources to check, back check, triple check my work all the time. There are many times when I am looking back over some work that I had done and find an inconsequential mistake. Finding the mistake plants the seed of doubt in my head "Wow if I missed something so trivial, could I have missed something big!" Then you procede to comb through your design with a fine tooth comb looking for the big mistake. I think that this is a good excercise becuase what you will find is that you probably never make the "big mistake". I see this as being a conscientious worker and you should view it as something that sets you apart from your peers. If you are upset by the mistakes that you make it is a good thing. To me this is a sign of someone who can be very successful in what they do. If the doctor performing my heart surgery did not feel bad about mistakes, then he is not going to be a good surgeon.
Sometimes though, reevaluating your current work does not always make you feel better. You may need to revisist past success to rejuvenate your attitude. For me, I drive around town and look at the bridges that I have created. No one can take these successes away from me. I can see it. You may need to do the same thing, even if it wasn't a success at your current job. Remember the good things and learn from the bad things.
To me, being successful is caring about your job. You want to do the best job that you can do. Nervousness is hard to overcome when you are not confident that what you are doing is right. You are just starting out in this career. NO ONE expects you to know the job inside and out on day one. A career is a life long pursuit that should be filled with learning everyday. If your company has any type of mentoring program, look into it. Everyone has these types of jitters over a new and challenging job. Talk with someone who has been through it before. Learn from them. Most people are more than willling to share with you their experience. I was lucky with my first job. I had plenty of people willing to help me through the maze.
I know this might not be the exact answer that you are looking for (I have a tendency to ramble...) but I hope this helps. Keep your chin up, learn the job and the confidence will grow. Once you get the confidence you need, you can be very happy with your career and you can learn to recover from the minor speed bumps along the way.
Quietguy