When I first started approaching girls, I was so much in my head that the girl was basically irrelevant to me. I was focusing on what I was doing, and to be honest while it's good to get out of your head.. This helps with the rejection. If I saw an attractive girl and approached her, I honestly didn't care if she rejected or not.. I was too busy congratulating myself for having the courage to do what a lot of guys simply can't. As you go you'll improve, you'll become a better conversationalist and will become more attractive personality and confidence wise.
I don't know if you watch Simple Pickup or any of those, but Kong had a video where he got rejected very harshly but at least 10 girls straight after each other one night, he just found it hilarious, because he wasn't aiming to try to impress them or get their number, he was aiming to go out, talk to some cute girls and enjoy himself... And if the girls happened to like that, great... If not, cool.