Do you want advice about whether or not your concerns are rational, or advice on how to overcome these concerns?
And by evidence-based advice, do you want studies? Because I think the specific case may be, well, too specific for evidence-based advice to be useful. Unless your anxiety is more generalized, at least.
I thought I made it clear in my post that I don't think my concerns are rational, but if they are I would like to take whatever steps are available to mitigate them, and not feel so crappy about it either way.
I feel similar anxiety in some other situations, but not very many of them. I find it a bit hard to believe that this problem is so incredibly specific that there is no useful reference class from which to derive advice.
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.