I'm a recent nursing school graduate. The feelings you are having are not uncommon I think many people worry while coming to the end of something as extensive as nursing school. I attended a 2 1/2 year BSN program and I very much valued my breaks over the summer to recooperate. Nothing is more rewarding than the realization that you are done!!
My advice for you is if you have a summer off from school you should definitely look into an internship before you finish nursing school. It helps soldify information you obtained throughout nursing school and looks great on a resume. I completed a summer internship at the U of I Hospitals & Clinics, great experience and helped me gain the job I will be starting there next month. When your doing your preceptorship for school I advise asking lots of questions and learning as much as you can!! If you develop a good relationship with your preceptor the learning opportunities are endless.
When it comes to preparing for NCLEX my advice is to not STRESS! Its a test (a big test none the less) but still just a test! I prepared for about 2 1/2 weeks for my NCLEX with a review course recommended by my school. I thought it was a great review and I ended up getting 75 questions on my NCLEX (minimum for an RN) and took about an hour and a half to take it! Found out two days later that I had passed!
I hope some of this information helps! Good Luck in your final semesters of nursing school and be proud of what you accomplished!!