The first of the preliminaries is the qualifications. And among these four, there are six. The sixth one is a shada, a firm faith in the teachings of the teaher and the scriptures. A firm faith means, i don't get it now, but if i persevere, i'll get it. It's not a you have to believe kind of thing. In fact, you must not believe. Ultimately, understanding is what is required.
Swami Sarvapriyananda teaches one of the shortest and most profound upanishads accompanied by Gaudapada's Karika. This lecture covers Mantra 1.