We all strive to improve our skills on a daily basis, and several times a year we are allowed to test our skills.
Don't kid yourself into thinking, "I do this every day. Why should I practice?"
Why? Because testing is NOT the same as the real-world environment in which we work. In the real-world environment, there are breaks, small pauses, misspeaks, breaths, variable speeds. In a testing environment, the speed is regulated and you get ONE CHANCE (at least in a realtime setting) to get everything right.
You might say, "Well, yeah, but at work, I get one chance." I disagree - you've already told your clients there may be errors or sound-alike words that come up, or phonetics, or a dropped period or comma; that it will be a clean transcript upon final delivery. In testing situations, every last detail must be perfect because you can't go back and fix it.
Five minutes at 180 words per minute is 900 words. Plus punctuation. Testing allows you to make 36 errors. That is all. And all it takes is a moment of distraction - say you didn't write a word correctly and you KNOW it, go back to fix it, make it worse - and you could potentially kill your chances for a passing grade.
Not to mention you may have just regular test anxiety. Nerves. Your heart is beating too fast. Your environment isn't familiar. Uncomfortable chair. Cold room. Bad night's sleep (that's mine this last time - woke up at 3:30 and couldn't go back to sleep). Bad breakfast. Any number of things.
What's the answer? Start practicing. NOW. Be honest with yourself. What do you need to work on? Is it your conflicts? Concentration? Speed? Take practice tests and gauge where you are. Don't wait until the last week before the test and think you can cram. This is NOT the kind of exam you can cram for.
In the end, certification gives you an added boost to your confidence (to some, to their paycheck as well!). Being prepared is key. See you in May - and this time I promise to be ready.