Study Pickup Artistry. The cold-blooded rational approach presented there will quell your anxieties.
The advice is good in general, but how exactly will it help in this specific case? For example, how reliably does reading "cold-blooded rational" texts reduce anxiety? It could easily have the opposite effect. Like: "Oh, to be successful with girls you have to be like this, and I can't imagine myself being like that... so I guess I have no chance." There; anxiety doubled. Now not only does one fear about rejection, but also that without developing the proper (possibly unsympathetic) personality, even the short-term successes are ultimat...
I started going out with a fantastic girl a couple of weeks ago. Everything is great, except that whenever I've sent her a text message or email requesting something and haven't received a response yet, I experience significant dysphoric anxiety, fearing that her response will be not just "no" but "no and I don't want to date you any more". This is due to brain chemistry or personal history, take your pick—either seems like a possible explanation to me. But there's certainly no evidence supporting the idea that this is likely to happen, nor is the anxiety helping me prevent it or helping me in any other way.
Does anyone have evidence-based advice, or pointers to same, on dealing with this kind of issue? It is the only splotch on what have otherwise been the best two weeks of my life.