Темная ночь не навек

Bad times will come to an end. See После грозы - ведро (П)

Cf: The darker hour is that before the dawn (Br.). The darkest hour is just before dawn (Am.). The darkest hour is nearest the dawn (Am., Br.). It is always darkest before /the/ dawn (Am., Br.). It's always dark before the sun shines (Am.). The longest night must end (Am.). The longest night will have an end (Br.)