I once visited a cave in the North of England where they took us deep underground and then turned off the lights. The guide told us that the darkness was such that our eyes would never adjust no matter how long we waited. When he did turn the lights back on he did so gradually. Normal light would have been blinding to our eyes.
The Psalmist says '...even the darkness will not be dark to you; the night will shine like the day, for darkness is as light to you.' (Psalm 139:12)
There is no darkness in our lives that our 'eyes' cannot adjust too. Waiting in the dark is never fruitless because the darkness is as light. I find that comforting because it gives me something constructive to do in the darkness. Instead of cursing it I can pray that my eyes adjust to the 'darkness that is as light.' in the light of that darkness who knows what I may see and learn. Instead of just waiting for the light I can gaze into the darkness for signs of God's handiwork.....and maybe, maybe I can dance.