Hey, DON'T PANIC!!!
I have been an EMT for just under a year, and I was the same way when I first started. I do not work as an EMT (for $$$), but I respond with the volunteer fire department where I live. I have learned to harness the terror! Also, you just has to know you can do it. Knowledge and Skill is a small fraction of what you actually need to do, confidence is HUGE!!! Also, when in doubt, fall back and punt. Go back to the basics and slow down and think. If you still feel like you're at a loss for what to do, practice with the equipment and with your skills. Are you nervous about the assessments and all? PassEMT (a video) is a great review! Just relax. I know its scary, but most importantly, you have to remember, it's not your emergency! Whoever called you needs your help, not the other way around. Also, don't worry too much about hurting tha patient! Often, there's no place to go but up.