Sorry to hear that she is not interested at the moment but you DEFINITELY did the right thing.
Otherwise you could have gone on indefinitely wondering how she felt and wondering if you should pursue her, or if she was "the one".
This part of the deal hurts and can make you sick - but you will look back and be glad this page is turned.
My suggestion is to close the chapter and move on. But I would not go and ask out every pretty girl you see or try to convince yourself of a new love interest. I would start doing things that interest you - whether it is exercise or taking an art class or joining a book club - pick something that you like that you can immerse yourself in. I can't say you will necessarily meet "the one" that way, but you will find joy in what you are doing, and you might make a friend or two along the way. I say that good things happen to people when they are doing what makes them happy, and people always seem more attractive when they are happy and self condifent. So close the book and open a new one.
You are young and you will be fine.
