Sadly, rejection is part of life. The good thing is, don't reject yourself or the confidence you had when you asked her out. Keep living, keep breathing and keep being you. There are much worse rejections than a person who does not want to go out with you. See life as a whole. We often times only see what's before us. Imagine the rejection of a job interview when your mortgage is months behind. Imagine a vital organ in your body rejecting. Imagine a judge's rejection your defense when you're innocent and you're sentenced to prison. Kind of makes that girl's rejection small, doesn't it? Love yourself, know yourself well enough to say, that nobody who rejects me, I never will. And, be your own greatest hero and inspiration. Sounds weird, but it does wonders for your self confidence.