Every so often we see someone else just like us. We see them do something or say something that just clicks. This isn't that common, and it's a cause for much happiness to find someone that you feel like you can talk to freely - someone who's got the same point of view, who you don't feel you have to explain yourself to.
This is followed by a period of discovery - of finding the many similarities, the numerous backgrounds you have in common, the loves and hates. Even those things which aren't held in common are seen as evidence of things you would have in common, but for differences in experience.
And then this tranquil mirror is shattered - one day we look at our new friend and realise they aren't quite the same as us. We find a slight imperfection in them, where what we thought was perfect accordance isn't quite as perfect as we thought. There's a moment of shock, of realisation that there will have to be disagreement. There's a fall from grace, a return to the real world, where dealing with people isn't fluid play, it's work.
We recover quickly from the fall - after all, we're used to dealing with people who are different. But there's now a tarnish on the relationship - you can't go back to innocence, and where there was this feeling of total trust, of belief in the other, there's now a fateful knowledge that the other person is just that, other, that the faith we have in them can be many things, but it can no longer be complete.
