He who learns must suffer. And even in our sleep pain that cannot forget falls drop by drop upon the heart, and in our own despair, against our will, comes wisdom to us by the awful grace of God.
AeschylusJustice, voiceless, unseen, seeth thee when thou sleepest and when thou goest forth and when thou liest down. Continually doth she attend thee, now aslant thy course, now at a later time. These lines are from a section of doubtful or spurious fragments.
Aeschylus