Whether an energy manifests as yin or yang, it has a beginning - a moment of sudden movement from stillness, a continuation - when the energy has a purpose, a direction, and it's unstoppable, and a finalisation - after the goal has been achieved and now the energy waits for another factor to set it in motion.
These stages represent the three cosmic functions: creation, maintenance, and destruction (in Hinduism: Trimūrti - the cosmic functions personified as a triad of deities: Brahma the creator, Vishnu the preserver, and Shiva the destroyer), which in astrology appear as the three modalities: cardinal, fixed and mutable.
