I need to learn to man up.... HELP!?

Ok I need to get the nerve to talk to this guy who was brave enough to ask me out in person and have me laugh in his face. (nervously laughed but you cant telll the difference.) So I need to know how to get nerver. :D D: Plzzz Its been killing me and I need to do it so please TELL ME HOW TO STOP BEING A COWARD!