Use when you've built a fixed method, stance, or plan and it's gone rigid — return to water: keep the intent, release the fixed form. Use to notice when 'discipline' has hardened into a dead hand.

The most striking agreement in the whole comparison. Both independently reach for WATER as the image of perfect adaptability — Sun Tzu for an army's dispositions ('just as water retains no constant shape, so in warfare there are no constant conditions'), Musashi for a swordsman's body. Formlessness is the shared core, arrived at from opposite scales.