Seal the openings, shut the doors, and until your last day you will not be exhausted. Widen the openings, interfere, and until your last day you will not be safe.
Under heaven all can see beauty as beauty only because there is ugliness. All can know good as good only because there is evil. Therefore having and not having arise together. Difficult and easy complement each other. Long and short contrast each other. High and low rest upon each other. Voice and sound harmonize each other. Front and back follow one another.