The source is a chapter from the book "Welcoming the Unwelcome" by Pema Chödrön, a Buddhist nun and teacher. The chapter focuses on the practice of bodhichitta, the awakened heart, a powerful motivation to awaken for the benefit of all living beings. The author argues that bodhichitta begins with a "broken heart", acknowledging the pain we all experience and recognizing our interconnectedness with all living beings. She then explores a range of practices that help cultivate bodhichitta, including overcoming polarization, practicing open awareness, and embracing difficult emotions and situations. The chapter emphasizes that even when we feel overwhelmed by suffering, or when we encounter "mission impossible" challenges, we can discover the limitless potential of bodhichitta and continue to move towards awakening through dedication and practice.