Sustainability refers to practices that can be maintained indefinitely without depleting resources or causing severe environmental damage. The document discusses how societies have moved away from more sustainable practices of the past through higher consumption, easy credit, and short-term thinking. It argues that to become sustainable again, societies must reduce waste and excess by using only what is needed, recycling, and shifting to a maintenance mindset rather than constant consumption. A sustainable society is possible and has been achieved before through balancing human activities with environmental protection. Strong leadership, communication, and collective action are needed to manage the transition.