How do you continue to have confidence when you are rejected?

Ok, so you see this hot girl and you dress well and tell yourself that you are good looking and that all you want to do is get a date with her. You end up having a good conversation, finding out she is single and you even get her number. Every time you ask her to go on a date, she refuses. Eventually you see her going out with another guy. How you do keep your self esteem up when you are rejected?