How to be more outgoing around new girls?

Ok so plenty of girls give me the eye ans hints to talk to them all the time, but I never do anything because I always.. well just not do it. I don't really I get nervous, it's just that I haven't done it in so long or got rejected enough when I approached a girl or two that gave no hint, that I just have this mindset that I won't talk to a girl. If I can get a new mindset like trial and error maybe I can succeed? Anyway so yesterday I saw a girl who gave me hints and she was already with another dude and STILL looking at me. Lost that chance. At a football game a girl said did I want to buy a raffle ticket and I said naa, she was smiling at me the ENTIRE time. Then when I walked off and she was still smiling and said it's only a dollar!! See if I was outgoing I could have said something like I might just buy one because you're cute.. see?