Keep calm! It's just an exam!
A lot of otherwise prepared students fare poorly in academic tests because they stress out and get nervous about taking them. If you are among such students, here are three ideas to help you combat these nervous feelings.
You know the material
You studied, right? (If you didn't, well... then you have bigger problems than dealing with exam stress) Assuming you did, assuming you have studied between each class, done your reading assignments and homework, and paid attention in class, then you should already know the answers to most of the questions on the test. Most of the questions will only require a regurgitation of information you have already received.
A lot of exam fear comes from students believing, "What if I forget anything?... what if I hit a question whose answer I don't know?" These are monsters under the bed most of the time. You know the answers.
The time limit is plenty of time
One hour may not seem like much time, but if you know the answers, answering questions should be relatively quick and easy. Instructors allot time for tests based on how long their students take on average to complete them, and the length of tests is also set with this time limit in mind.
Don't focus on the clock. Just take each question one at a time, and you may be surprised at how quickly you work through most tests.
Also, no need to worry that the instructor didn't give you enough time. If it's not enough time for you, it usually won't be enough time for everyone else either, and in the rare situation where most of the class fails to finish on time, the instructor, unless he/she is a sadist, will have to take a second look at the grading scale and the content of the exam. But if you focus more on the exam than the clock and your own stress, you should finish with time to spare even if you're slower than most.
Most of the problem is in your head
It's amazing the impact the human mind can have on performance. Stress, fear, impatience, self doubt and lack of discipline often produce failure for people who would otherwise succeed.
You may have more than enough command of the material, but then you stress about the forthcoming test, and your thoughts of impending dread start to affect your mood, your outlook and, eventually, your thinking process. It makes you look at the clock each minute, wasting time and brainpower worrying about how you're going to get through this... instead of using them to work through the questions and produce correct answers.
For the most part, human beings can control their emotions, or learn to work through them, to press forward despite their fears and get the job done. If you're going to succeed in the real world, you need to learn how to handle adversity, and that includes taking tests well without letting your own stress get to you. After all, if the thought of taking a test is enough to break you, how are you going to be able to handle the deadlines and responsibilities of a job?
Consider working through your exam anxiety as part of the learning process, as a step you need to take forward to grow as a person, and you will have taken a huge step forward in life.