I'm the opposite. If I don't think a person likes me, I instantly label them as worthless to me. Even with my most fervent schoolboy crushes, the guaranteed way to get me back to normal was to explain that the object of my desire didn't feel the same way. There would follow a few days of mourning and then I'd be allright again.
Also I find it hard to imagine how anybody could get into that position......I guess one person could be sexually attracted to another without any reciprocation, but that's just a physical thing and shouldn't give anybody sleepless nights. But as for the other part of the mating equation - relating - if I'm relating well to a lady, it seems absurd to imagine that she wouldn't also be relating to me.....there seems no point in getting all gooey about somebody who isn't already reciprocating my gestures of warmth, interest. I think that with experience you get to know when you're dealing with a future partner, there's a look and feel about it, though I always doubt the evidence of my own senses until we've slept together. And in spite of what I've said, I can still catch myself putting women on pedestals, as if an honest appraisal of her personality was somehow unseeemly. So yes, I suppose I do know what you're talking about. I think it's important to use a healthy bit of cynicism when thinking about individuals who might be OK as partners, even if it's not very romantic. It's wise to look ahead.