Hey wildgopher, (great name btw)

I also can't give you any advice on how to stop this way of thinking. But...I can identify...It's one thing to say that people are fallible and will inevitably dissapoint us if we place them on pedestals, it's another to put that into practice. The way I've been doing this lately is to avoid any and all expectations... (simply dissapointments waiting to happen). If I can separate the perceived person from the real person that's would be wonderful! Unfortunately I don't know how to do that, I'm just not at that place yet.

Another thing though, having idealizations that a person is perfect and has no qualities that are less than redeeming makes me out to be less than (even if I'm not doing it consciously). The more I idealize someone, the more I'm deflating myself. I place too much value on the person and then my mind will gravitate toward that idealization (maybe they will idealize me too? because what else do I want but to have myself validated by someone who I think is so amazing? I personally have a hard time validating myself and thus gravitate toward self-deprication and negative thoughts about myself.) Once this person lets me down, I will be dissapointed even more (i thought they were perfect? how can someone so fallible now validate me?) I have to remember I'm pretty cool, too...(not perfect, not a piece of crap either) and the same goes for the other person.

Again, this is very hard to put into practice, but cognitive behavioral stuff works around changing thinking patterns...Try remembering experiences you've had with this person (even if you can't have current ones) write on a piece of paper: reality vs. idealization in two columns. Write down the facts vs. the fabrications.
reality: she's nice. she has strong values. idealization: she has never done anything wrong. she has never hurt someone. reality: she's smart. idealization: she's a genius! (is her iq over 250? probably not)

Maybe writing it down can help us see how much we are denying reality?

Anyway sorry for rambling, I got off on some thoughts there. Also, I am only speaking from my own experiences.

Like others have said at least you can see what you're doing...We can't make a change until we realize what we have to change. It takes a lot to admit where we are at fault (just means we're fallible too, but not less than).