Why does truth arise through mistakes?

Žižek in The Most Sublime of Hysterics: Hegel with Lacan:

The idea that one is able from the outset to account for error, to take it under consideration as error, and therefore to take one’s distance from it, is precisely the supreme error of the existence of metalanguage, the illusion that, while taking part in illusion, one is somehow also able to observe the process from an ‘objective’ distance. By avoiding identifying oneself with error, we commit the supreme error and miss the truth, because the place of truth itself is only constituted through error. To put this another way, we could recall the Hegelian proposition which can be paraphrased as ‘the fear of error is error itself: the true evil is not the evil object but the one who perceives evil as such.