The present book contains the revised transcripts of his teachings on mental training, which he gave at the Tibetan Center between 1998 and 2000. Geshe-la not only incorporates the knowledge of his tradition here but also shares his personal experiences with Mahayana practice. His great talent for "translating" traditional Buddhist content for the West and conveying it with wisdom, humor, and foresight is evident in the included questions and answers. He had wished for his teachings to eventually become a book. We are pleased to have been able to fulfill this wish about two years after his passing. The teachings represent the greatest treasure that Geshe Thubten Ngawang has left behind. Those who not only read them but also apply them can attain inner contentment and genuine happiness.