While studying, read answers to essay questions in the study guides. Study the content and format of the answers. For some people, writing out all potential essay questions is helpful. Consider getting help in preparing for the exam either through one of the established review courses, computer assisted software or self-study. If you have to travel some distance for the exam, leave early and arrive the day before.
Bad experiences are usually the result of poor preparation.
Be prepared, be confident and be positive in your attitude. Do not study heavily the night before the exam or the nights between. Consider taking a break for a few minutes during each session of the exam. While it may be true that you will need most, if not all, of the time allowed, a short break can be very refreshing.