Everyone talks about it, everyone believes that they are fulfilling it. The talk is about sustainability, but why do many believe to be sustainable, although the lifestyles and life realities diverge so strongly in regard of sustainability? Sustainability is for many people something subjective, due to the fact that the term is not protected by name law, it is up to everyone to interpret sustainability in their own sense. However, the last 70 years have shown that humans are moving further and further away from sustainability. The sustainability sciences have long been aware that we need to change the ""human Earth's system"" in order to follow the principles of sustainability. But why is a clear and understandable definition of sustainability so important? Only through the framework of a qualitative definition human actions, supply chains, products and services can be aligned with sustainability. Decent development for all is not only a demand of the United Nations, it is a daily challenge for all of us. Due to the increasing inequality within society, as well as the crossing of planetary boundaries, the Earth system is getting more and more out of control. The climate crisis as well as various weather extreme events, which occur in a temporal interval, which does not let an adaptation become possible (as well as suggests that this frequency is caused by the human acting) are first harbingers of new Earth cycles, which will affect in the future the human life on earth considerably. We have arrived in the new Earth epoch of the Anthropocene, it is up to humans themselves to choose the amplitude of Earth change. Planetary Boundaries as well as the social indicators of the Sustainable Development Goals (SDGs) give us a first roadmap how sustainable development as well as sustainability can look like globally. The European Green Deal as well as the invention of first national supply chain laws can be interpreted as a step in the right direction, but is it enough to take steps at this pace if we already miss the 1.5° target in less than 7 years? The aim of this paper is to evaluate the past as well as the existing concepts of sustainability. Based on this, the concepts of Planetary Boundaries and Doughnut Economy will be used to derive a clear and comprehensive definition of sustainability that deliberately narrows the scope and thus allows for a development towards more sustainability. Humanity decides, whether we create the "Great Decoupling" or have completed the "Great Collapse" until the end of the century.