Guna
गुण (guṇa)
The three strands - clarity, agitation, inertia - whose shifting blend gives every state its texture.
Guna means strand or quality, and Samkhya philosophy weaves the whole of nature from three of them: sattva - clarity, lightness, balance; rajas - energy, agitation, drive; tamas - mass, darkness, inertia. Everything manifest, including moods and mornings, is a blend.
The scheme is not a moral ranking so much as a physics of experience. Rajas is needed to act; tamas is needed to sleep and to hold form; sattva is needed to see. Trouble comes from proportion and timing - agitation at midnight, inertia at noon.
Its practical gift is diagnostic. Asking what am I feeling? often invites a novel; asking which guna is ahead right now? invites an answer - and each answer has known remedies. The arts of adjusting food, effort, rest, and company by guna are the ancient forerunners of every energy-management method since.