Second, if you make a mistake in the classroom, it doesn't count. The only grade that counts in most law school classes is the final. Relax and make mistakes. It will help you in the exam to know your weak points. Third, hundreds of thousands of students have sat where you're sitting now and have survived and thrived.
Some people purposefully create stress as a motivator for themselves.
They freak out at the workload and use it as a way to bond with other students. Stay away from the people who are stressing out. Stress creates stress, and you want to focus your energies on studying, not stressing out. Although grades are important, it's also important to put them in perspective. One key factor in getting good grades is to forget about them and concentrate on the learning.