Hyperactivity and restraint (kang-hai cheng-zhi)

In Chinese medicine, the principle of hyperactivity, harm and restraint among the five phases. The Neijing holds that when a phase is hyperactive it causes harm, but the phase restraining it checks the excess, and this restraint sustains normal generation and transformation (亢則害，承迺制，制則生化). It explains how the five phases self-regulate to maintain dynamic balance.