Practice, Practice, Practice.....that goes for clinicals and for classes. As far as clinicals go. We had a lab pack we needed to use that had everything in it. It sounds corney but set up a station at home and practice. As far as the tests what I did was read the material before class and make a list of any questions you may have. Follow along w/ lecture and then read the material and lecture notes again but together and compare the 2 for major points. Then I got an NCLEX book called Fundamentals Success for the first semester and just the Saunders Comprehensive guide for the rest of school and that helped with the different style of questions in nursing school vs. other classes.
You're not a screw-up. As others have stated, nursing school is just a different way of thinking
Good luck