Bullshit. A girl can reject a guy for any number of reasons. Some of the most charismatic "PUAs" (if you want to call them that) I know have gotten blown the fuck out for absolutely no reason. Well, obviously there's a reason, but it has nothing to do with the guy. For instance, some women reject a man's approach because:
1) She has shit to do. She's on a time table and doesn't have time to stop and chat. She's late for work, a meeting, appointment, etc... Believe it or not, some women DO value their careers & responsibilities over random sexual encounters. Let's get fucking real.
2) She feels fucking depressed/sad/hungover. I've seen girls in my social circle reject guys due to feeling like shit and then later regretting it. For the poor guys, it seems like they did something wrong, when in reality, the girl was actually just super insecure about her emotional state and couldn't deal with keeping up with a highly engaging guy. It is sometimes easier for her to just block the approaching dude out then trying to readjust her state (especially if she's super depressed, stressed, etc...).
3) She just isn't attracted to you. It's almost heresy in a PUA forum to say this. A lot of PUAs have this ridiculous notion that - armed with enough social firepower - you can attract ANY woman, ever. Sorry to say, but some women just won't be attracted to you, regardless of what you do (it won't matter if you have a million girls on your dick and social proof out the roof). Have you ever met a SUPER hot woman that just didn't turn you on? LIke, she's REALLY pretty, but she just didn't get you aroused? It's possible to be a highly attractive man and still not be genetically/emotionally/physically compatible with some women. That's jus the reality of it. It's not your fault, it's natures. In fact, if you read about some of the greatest Pickup artists ever (even Casanova), they usually run into that one girl who was impervious to "game."

My friend - there is no easy way to deal with rejection. However, there are a certain mindsets you can adopt to ease the blow of it:
1) Don't use women as the source of your validation. If sleeping with girls is a huge part of your self-esteem, it's time to refocus your priorities in life. Derive validation and self-esteem from other areas in your life. Once you do this, rejection won't be as terrible to deal with because your entire identity won't be riding on your sexual success.
2) Approach women from a "buyer" mentality, not a "seller." Many guys approach women wondering what actions they can take to turn her own, get a reaction out of her, etc... Basically, they're trying to pitch themselves to strangers. This "salesmen" mindset is incredibly dangerous for beginning PUAs, although it's perpetuated by the PUA culture thanks to terms like, "closing", etc... What you need to do is approach women with the mindset of, "I wonder if she's as awesome as she is gorgeous." Screen the fuck out of her, and make sure she's a woman that actually turns you the fuck on. Don't settle for anything less.
3) Like James Marshall said, it's best to not mask the pain of rejection with "alpha" behavior. Instead, I would recommend you adopt a mindset of humor. It can be funny to get rejected! Just the absurdity of approaching strangers in public and trying to turn them on is already fucking hilarious, and when they say, "no" it should be met with lighthearted amusement.

Personally, I use rejection as a chance to act as absurd and self-amusing as possible. After I've pretty much determined there's no way this chick is going for me right now (or if I determine I don't really like her anyway so her rejection was a godsend), I like to mess her head a bit and just have as much fun with it as possible. In fact, I've actually pulled a few girls this way (post-rejection).

Moments like those make me realize that by sticking within the boundaries of PUA, I'm actually hurting myself more than if I simply lose the whole, "IOI, DHV, CALIBRATION, SOCIAL PROOF" bullshit and just express myself fully.