How to turn fear into excitement?

I really like this girl, and she is nice but i keep thinking she is too attractive for me or that she is out of my league because she is too popular. I mean I have never met anyone who fills me with such emotion just by looking at them. I'm a nice, funny guy but i have been too shy in the past. Well i really really want to talk to this girl, just have a nice conversation. If it goes well, then i will keep talking to her. If not then at least i know it's not meant to be.

Anyway, whenever it's about the time i'm going to approach her, i really get butterfly's and become nervous, even though i know it will be fine. How can i turn those butterfly's into excitement butterfly's?