Acceptance is a fundamental process in Acceptance and Commitment Therapy (ACT) that plays a crucial role in addressing the challenges of the 6th Mass Extinction and climate change. It involves embracing difficult thoughts and emotions related to environmental crises instead of avoiding or denying them. Such avoidance often leads to widespread denial of scientific evidence and disconnect from distressing realities, hindering society's ability to identify and implement solutions. Non-acceptance creates psychological filters that obscure the urgency of these issues, diminishing the capacity for creative engagement and collective action. The longer humanity ignores its role in environmental degradation, the less likely it is to implement meaningful changes. Acceptance is not passive; it serves as a catalyst for values-based action, allowing individuals to confront their emotions, such as grief and guilt, regarding planetary decline. It enables people to make choices aligned with their values, fostering psychological flexibility necessary for tackling adversity. Furthermore, acceptance serves as the foundation for the other core processes of ACT—cognitive defusion, mindfulness, self-context, values clarification, and committed action—highlighting its essential role in fostering meaningful change during this global crisis.