Shakyamuni Buddha advised dharma students to rely on the teachings and not on the teacher. Dzongsar Khyentse Rinpoche explains how this statement does not in the least contradict the importance of the teacher-disciple relationship.
Just like a rainbow, or the reflection of a face in a mirror, all phenomena are both present and not present, yet dualistic human beings easily fall into the misconception that phenomena truly exist, or alternatively that nothing exists. For the student of Buddhism, learning about the truth is paramount, and at the most absolute level this means understanding non-duality. In Vajrayana Buddhism, the teacher is the entire path and guru yoga involves the student and the teacher becoming inseparable, leading the student to understand that the inner guru is none other than their own mind.