Its completely normal to feel anxious when you're on the stepping stone of your career. But don't put too much pressure on yourself. Enjoy the ride and take in the new experience as it would be important for your professional growth. At the same time relax and put your brain at ease as that would make the grasping of the concepts easy and keep your mind clear for productive ideas. If you are still unsure about your job then best to go for a counseling session so that you can get some more clarity on your goals.