Literally, "Trouble is like playing the reed of the flute. When you are strong, it becomes weak but when you becomes weak, it becomes strong."
"Trouble is like blowing the reed the reed of the flute. When you blow hard, it bends in malleability but springs back when the pressure is gone."
More polishing and figuratively:
Troubles are flexible and yet resilient. When you flex your muscles, they wane but wax if you retreat.