If you say something or do something that your date/prospect doesn't like it could be an indicator that you have values/behaviours/habits that your date would find completely incompatible with him/herself. Most likely it's an incompatible personality that causes the "one look" that brings you down, not bad luck. (And yes, if you goof because you're nervous, perhaps your prospect isn't interested in someone who's inexperienced in social situations or with the opposite sex. Consider if you really want to be with someone unforgiving of those traits.)

You can almost always get a second chance. It doesn't come from begging for it or pouting in a corner; you have to WIN it. An acquaintance of mine was fat, arrogant, and socially abrasive when I met him. I wouldn't have been interested. He lived abroad for a while and when he came back he was the most gorgeous and charming man. Just because I would have rejected him before doesn't mean my lack of interest was permanent no matter what. This acquaintance made some changes to himself and he became irresistible in my eyes.

Circumstances change all the time, and with that, people's idea of who they are and aren't interested in. Let's face it: the club hottie that wouldn't glance at you earlier in the night is by closing time boozed up and wanting to take you home. Circumstances can change all within the space of a few hours.

If you blow your first chance with a person and you really think you could make a connection with him/her you can try winning a second chance. Do something to capture his/her attention. Show off a talent of yours. Send a token to him/her that shows a side of your personality s/he hasn't seen yet. These things can work... They just can't guarantee that you won't experience a second rejection from the same person. (Just because you think you'd be great with someone doesn't mean the other person feels the same way about you.)

I'm also in disagreement with any notion that it's rejection or happily ever after. If the object of your desire rejects you it doesn't mean you have lost out on happily ever after with that person. The remote possibility of happily ever after, perhaps. But chances are you might have had a couple more dates with that person before one of you decides that you're not right for each other... Or maybe you'll spend two years loving that person and investing yourself financially and emotionally before s/he or you decides, "nope! I don't want to do this anymore." In my opinion a blanket happily-ever-after outcome from a first or second date is the most remote of all possibilities.

I particularly enjoy movies that I think are representative of real life. I'd probably think Hitch was heavy on the "entertainment" side versus the "slice-of-life/introspection" side.