being scared is a good thing - it shows you take the responsibility seriously.
You can do it and it does get easier as you go along, there were times i did not think i would survive my first weeks, let alone months or a year - but i did and it gets a little less overwhelming and you gain a little more confidence each day. Just keep telling yourself you can do it, believe in yourself and dont be scared to ask for help, no one starts out an experienced nurse, everyone starts right where you are now.
"Courage isn't the absence of fear. It is moving forward in spite of it." I love this quote, says it all really.