It's going to take you a few days and a few passes at the menu to get your moves down, and get your mise en place the way you like it. It's one thing to know each plate, it's another to see them pass through enough to be able to cope with different combinations of orders, getting them all to come up when they are needed.
It will be stressful at first, it is for nearly everyone. Then, all of a sudden, you are on autopilot, in the groove.
There are two possible reasons why you are in this position now:
1. The chef/sous thinks you can handle it.
2. You are the only/last guy available, or the other choices are to horrible to contemplate.
Don't feel bad about number 2. I have advanced in my career mostly because of it.
Simply be the last man standing when everybody else falls down, drifts away, etc. It's hardly a negative, after all, YOU stuck with it right? YOU supported your chef and your crew right? You earned it, so what if it's by default? All those big talking, flash in the pan guys that you prepped for? You have their job now.