Look — you did the right thing. You had the courage, as boogle said, to ask your friend out on a date, so you should feel great about that even though she said no. Having regrets for never having tried would be much, much, much worse than if you tried and got shot down.
So much of life is getting up to the plate and giving that proverbial ball your best swing. Now, while you may be disappointed, you can have peace of mind (which I hear in your post) that you tried and there is nothing to do any more.
You are a great guy and you should get out there and find someone who wants to be your girlfriend. Believe it or not, you’re going to be a better boyfriend when you become a boyfriend, for having gone through this.
Good luck — and let me know when you meet someone great!