Letters from a Stoic 92 : 18

Similarly, obstacles take nothing away from virtue; it is no smaller, but merely shines with less brilliancy. In our eyes, it may perhaps be less visible and less luminous than before; but as regards itself it is the same and, like the sun when he is eclipsed, is still, though in secret, putting forth its strength. Disasters, therefore, and losses, and wrongs, have only the same power over virtue that a cloud has over the sun.