From the Preface by 17th Karmapa, Ogyen Trinley Dorje: Some people recite the Eight Verses only as a prayer or aspiration, but that was not Geshe Langri Thangpa's intention. He envisioned the text being used as a handbook for the practice of mind training. In these verses, he tells us precisely what we have to do. Through them, he teaches us how to visualize, how to prepare our mind, how to focus, and how to analyze. They cover all the crucial points for taming one's mind and developing bodhicitta. They are not just something to be understood intellectually or paid lip-service; they have to be put into practice.
From the introduction: The Gyalwang Karmapa has taught Geshe Langri Thangpa's Eight Verses of Training the Mind on several occasions. Though short, this text gets to the core of Mahayana practice, and each time he teaches it, he emphasizes different themes. In this particular teaching, he stressed how we need to bring our practice to bear on the difficulties that face us in our life and our dharma practice -- an issue that all practitioners must face if their practice is to be effective.