When tempered beyond its natural state, the finest blade will lose its edge. Even the hardest tempered sword, against water, is of no avail. It will shatter if struck against a rock. When untangled by its cutting edge, a cord lies in little pieces, rendering it useless.
Just as the finest sword maker tempers the finest blade not only with fire but with his experience, so the wise one, with wisdom, tempers the intellect. With patience, tangled cord may be undone, and problems which seem insoluble, resolved.