Everyone has given great answers here, I still get butterflies on the way to the airport, part of the thrill.
A story, I was at a focus group with a bunch of pilots, probably about a year ago, there were about 25 seasoned pilots there. This was a marketing study for a company thinking about building a new airplane. Sometime during the questions a discussion came up. The question was, how long did it take after you passed your ppl check ride, before you were completely comfortable flying by yourself. Now these were seasoned pilots, who fly some impressive airplanes. The consensus was that it took about 50 hours or so after getting your license to feel really comfortable in the airplane alone. I was really surprised that everyone felt this way, I thought I was the only one.
So OP, as others have said, nervousness, or butterflies, are a good thing, it means you have a healthy respect for what you are doing and treating it as it should be treated. You will get more and more comfortable as you fly so fly as often as you can. Remember this, your CFI would not let you go if he didn't know you were ready. And with good pilots, the CFI always knows the pilot is ready before the pilot himself. Have fun!
