Used to light, one must also get used to the dark.

[in Plato's Republic] "the ideally ordered polis, fails not because of malevolent or external forces, but because of its own complexity. That is a true statement concerning something we all know to be the reality of any humanly planned economy: be the rationality of the planning ever so highly developed, in the execution of it there is always the power of coincidence, and above all, there is always human shortcoming. Because we are human beings, not because we planned mistakenly, even an ideal self-sustaining organization in full accord with the plan for it will nevertheless go under in the rolling seas of historical life. To say this is not at all to deny the task of reason to shape action reasonably. …human reason is not restricted to the realm of utopia and strict ideal order. On the contrary, it is fully capable of expanding into the historical world of vague regularities. The disorder of human things is never complete chaos. Ultimately this disorder represents the periphery of a sensibly ordered universe that under any circumstances would have its periphery. … In respect to interpreting the allegory of the cave …this wonderful and many-layered metaphor… [the] theme is the blinding by the brightness that befalls those accustomed to the dark, and conversely, the blinding of those who leave the brightness and enter the dark. … One must not only get used to the light; one must also get used to the dark. "

Hans-Georg Gadamer, "The Polis and Knowledge of the Good" in The Idea of the Good in Platonic-Aristotelian Philosophy (Yale University Press, 1986) p73. English translation by P. Christopher Smith.